diff --git a/lib/StyleDictionary.js b/lib/StyleDictionary.js
index e613ad6ca..a602dc7da 100644
--- a/lib/StyleDictionary.js
+++ b/lib/StyleDictionary.js
@@ -49,10 +49,6 @@ import cleanActions from './cleanActions.js';
 const PROPERTY_VALUE_COLLISIONS = GroupMessages.GROUP.PropertyValueCollisions;
 const PROPERTY_REFERENCE_WARNINGS = GroupMessages.GROUP.PropertyReferenceWarnings;
 
-// const TEMPLATE_DEPRECATION_WARNINGS = GroupMessages.GROUP.TemplateDeprecationWarnings;
-// const REGISTER_TEMPLATE_DEPRECATION_WARNINGS = GroupMessages.GROUP.RegisterTemplateDeprecationWarnings;
-// const SASS_MAP_FORMAT_DEPRECATION_WARNINGS = GroupMessages.GROUP.SassMapFormatDeprecationWarnings;
-
 /**
  * Style Dictionary module
  *
diff --git a/lib/common/formatHelpers/getTypeScriptType.js b/lib/common/formatHelpers/getTypeScriptType.js
index 3c81768d9..40ad40e9b 100644
--- a/lib/common/formatHelpers/getTypeScriptType.js
+++ b/lib/common/formatHelpers/getTypeScriptType.js
@@ -10,7 +10,6 @@
  * CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions
  * and limitations under the License.
  */
-import { unique } from '../../utils/es6_.js';
 
 /**
  * Given some value, returns a basic valid TypeScript type for that value.
@@ -72,11 +71,13 @@ function getArrayType(passedArray) {
     if (passedArray.every((v) => getTypeScriptType(v) === firstValueType)) {
       return firstValueType + '[]';
     } else {
-      return `(${unique(
-        passedArray.map((item, index) => {
-          const isLast = passedArray.length === index + 1;
-          return `${getTypeScriptType(item)}${!isLast ? ' | ' : ''}`;
-        }),
+      return `(${Array.from(
+        new Set(
+          passedArray.map((item, index) => {
+            const isLast = passedArray.length === index + 1;
+            return `${getTypeScriptType(item)}${!isLast ? ' | ' : ''}`;
+          }),
+        ),
       ).join('')})[]`;
     }
   }
diff --git a/lib/common/transforms.js b/lib/common/transforms.js
index abb3e917f..373dda09e 100644
--- a/lib/common/transforms.js
+++ b/lib/common/transforms.js
@@ -13,9 +13,16 @@
 
 import Color from 'tinycolor2';
 import path from '@bundled-es-modules/path-browserify';
-import { kebabCase, camelCase, snakeCase, upperFirst } from '../utils/es6_.js';
+import {
+  camelCaseTransformMerge,
+  snakeCase,
+  paramCase as kebabCase,
+  camelCase as _camelCase,
+} from 'change-case';
 import convertToBase64 from '../utils/convertToBase64.js';
 
+const camelCase = (str) => _camelCase(str, { transform: camelCaseTransformMerge });
+
 const UNICODE_PATTERN = /&#x([^;]+);/g;
 
 function isColor(token) {
@@ -281,6 +288,9 @@ export default {
   'name/cti/pascal': {
     type: 'name',
     transformer: function (token, options) {
+      const upperFirst = function (str) {
+        return str ? str[0].toUpperCase() + str.substr(1) : '';
+      };
       return upperFirst(camelCase([options.prefix].concat(token.path).join(' ')));
     },
   },
diff --git a/lib/filterTokens.js b/lib/filterTokens.js
index ce9e390ac..2ba4305c9 100644
--- a/lib/filterTokens.js
+++ b/lib/filterTokens.js
@@ -10,14 +10,13 @@
  * CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions
  * and limitations under the License.
  */
-
-import { reduce, isObject, filter as filterUtil, assign, isEmpty } from './utils/es6_.js';
+import { isPlainObject } from 'is-plain-object';
 
 /**
  * Takes a nested object of tokens and filters them using the provided
  * function.
  *
- * @param {Object} tokens
+ * @param {Object|undefined|null} tokens
  * @param {Function} filter - A function that receives a property object and
  *   returns `true` if the property should be included in the output or `false`
  *   if the property should be excluded from the output.
@@ -27,45 +26,26 @@ import { reduce, isObject, filter as filterUtil, assign, isEmpty } from './utils
 function filterTokenObject(tokens, filter) {
   // Use reduce to generate a new object with the unwanted tokens filtered
   // out
-  return reduce(
-    tokens,
-    (result, value, key) => {
-      // If the value is not an object, we don't know what it is. We return it as-is.
-      if (!isObject(value)) {
-        return result;
-        // If the value has a `value` member we know it's a property, pass it to
-        // the filter function and either include it in the final `result` object or
-        // exclude it (by returning the `result` object without it added).
-      } else if (typeof value.value !== 'undefined') {
-        return filter(value) ? assign(result, { [key]: value }) : result;
-        // If we got here we have an object that is not a property. We'll assume
-        // it's an object containing multiple tokens and recursively filter it
-        // using the `filterTokenObject` function.
-      } else {
-        const filtered = filterTokenObject(value, filter);
-        // If the filtered object is not empty then add it to the final `result`
-        // object. If it is empty then every property inside of it was filtered
-        // out, then exclude it entirely from the final `result` object.
-        return isEmpty(filtered) ? result : assign(result, { [key]: filtered });
-      }
-    },
-    {},
-  );
-}
-
-/**
- * Takes an array of tokens and filters them using the provided function.
- *
- * @param {Object[]} tokens
- * @param {Function} filter - A function that receives a property object and
- *   returns `true` if the property should be included in the output or `false`
- *   if the property should be excluded from the output.
- * @returns {Object[]} tokens - A new array containing only the tokens
- *   that matched the filter.
- */
-function filterTokenArray(tokens, filter) {
-  // Go lodash!
-  return filterUtil(tokens, filter);
+  return Object.entries(tokens ?? []).reduce((acc, [key, value]) => {
+    // If the value is not an object, we don't know what it is. We return it as-is.
+    if (!isPlainObject(value)) {
+      return acc;
+      // If the value has a `value` member we know it's a property, pass it to
+      // the filter function and either include it in the final `acc` object or
+      // exclude it (by returning the `acc` object without it added).
+    } else if (typeof value.value !== 'undefined') {
+      return filter(value) ? { ...acc, [key]: value } : acc;
+      // If we got here we have an object that is not a property. We'll assume
+      // it's an object containing multiple tokens and recursively filter it
+      // using the `filterTokenObject` function.
+    } else {
+      const filtered = filterTokenObject(value, filter);
+      // If the filtered object is not empty then add it to the final `acc`
+      // object. If it is empty then every property inside of it was filtered
+      // out, then exclude it entirely from the final `acc` object.
+      return Object.entries(filtered || {}).length < 1 ? acc : { ...acc, [key]: filtered };
+    }
+  }, {});
 }
 
 /**
@@ -84,9 +64,13 @@ export default function filterTokens(dictionary, filter) {
   if (!filter) {
     return dictionary;
   } else {
-    return {
-      allTokens: filterTokenArray(dictionary.allTokens, filter),
-      tokens: filterTokenObject(dictionary.tokens, filter),
-    };
+    if (typeof filter !== 'function') {
+      throw new Error('filter is not a function');
+    } else {
+      return {
+        allTokens: (dictionary.allTokens ?? []).filter(filter),
+        tokens: filterTokenObject(dictionary.tokens, filter),
+      };
+    }
   }
 }
diff --git a/lib/register/transformGroup.js b/lib/register/transformGroup.js
index 479396b63..beee04b56 100644
--- a/lib/register/transformGroup.js
+++ b/lib/register/transformGroup.js
@@ -11,8 +11,6 @@
  * and limitations under the License.
  */
 
-import { isArray } from '../utils/es6_.js';
-
 /**
  * Add a custom transformGroup to the Style Dictionary, which is a
  * group of transforms.
@@ -36,7 +34,7 @@ import { isArray } from '../utils/es6_.js';
  */
 export default function registerTransformGroup(options) {
   if (typeof options.name !== 'string') throw new Error('transform name must be a string');
-  if (!isArray(options.transforms))
+  if (!Array.isArray(options.transforms))
     throw new Error('transforms must be an array of registered value transforms');
 
   options.transforms.forEach(
diff --git a/lib/transform/config.js b/lib/transform/config.js
index 8ed4265cd..ab53dd4a3 100644
--- a/lib/transform/config.js
+++ b/lib/transform/config.js
@@ -11,11 +11,10 @@
  * and limitations under the License.
  */
 
-import { clone, matches } from '../utils/es6_.js';
+import { isPlainObject } from 'is-plain-object';
 import deepExtend from '../utils/deepExtend.js';
 import GroupMessages from '../utils/groupMessages.js';
 
-const TEMPLATE_DEPRECATION_WARNINGS = GroupMessages.GROUP.TemplateDeprecationWarnings;
 const MISSING_TRANSFORM_ERRORS = GroupMessages.GROUP.MissingRegisterTransformErrors;
 
 /**
@@ -29,7 +28,7 @@ const MISSING_TRANSFORM_ERRORS = GroupMessages.GROUP.MissingRegisterTransformErr
  * @returns {Object}
  */
 export default function transformConfig(platformConfig, dictionary, platformName) {
-  const to_ret = clone(platformConfig);
+  const to_ret = { ...platformConfig }; // structuredClone not suitable due to config being able to contain Function() etc.
   to_ret.log = platformConfig.log ?? dictionary.log;
 
   // The platform can define either a transformGroup or an array
@@ -123,6 +122,21 @@ None of ${transform_warnings} match the name of a registered transform.
           throw new Error("Can't find filter: " + file.filter);
         }
       } else if (typeof file.filter === 'object') {
+        // Recursively go over the object keys of filter object and
+        // return a filter Function that filters tokens
+        // by the specified object keys.
+        const matchFn = function (inputObj, testObj) {
+          if (isPlainObject(testObj)) {
+            return Object.keys(testObj).every((key) => matchFn(inputObj[key], testObj[key]));
+          } else {
+            return inputObj == testObj;
+          }
+        };
+        const matches = function (matchObj) {
+          let cloneObj = { ...matchObj }; // shallow clone, structuredClone not suitable because obj can contain "Function()"
+          let matchesFn = (inputObj) => matchFn(inputObj, cloneObj);
+          return matchesFn;
+        };
         ext.filter = matches(file.filter);
       } else if (typeof file.filter === 'function') {
         ext.filter = file.filter;
diff --git a/lib/transform/object.js b/lib/transform/object.js
index 1b0c296b9..641fe606f 100644
--- a/lib/transform/object.js
+++ b/lib/transform/object.js
@@ -11,7 +11,7 @@
  * and limitations under the License.
  */
 
-import { isPlainObject, pull } from '../utils/es6_.js';
+import { isPlainObject } from 'is-plain-object';
 import usesValueReference from '../utils/references/usesReference.js';
 import getName from '../utils/references/getName.js';
 import transformToken from './token.js';
@@ -26,7 +26,7 @@ import tokenSetup from './tokenSetup.js';
  * @private
  * @param {Object} obj
  * @param {Object} options
- * @param {Object} [transformationContext={}]
+ * @param {Object} [ctx={}]
  * @param {Array} [path=[]]
  * @param {Object} [transformedObj={}]
  * @returns {Object}
@@ -34,13 +34,12 @@ import tokenSetup from './tokenSetup.js';
 export default function transformObject(
   obj,
   options,
-  transformationContext = {},
+  { transformedPropRefs = [], deferredPropValueTransforms = [] } = {},
   path,
   transformedObj,
 ) {
   transformedObj = transformedObj || {};
   path = path || [];
-  const { transformedPropRefs = [], deferredPropValueTransforms = [] } = transformationContext;
 
   for (const name in obj) {
     if (!obj.hasOwnProperty(name)) {
@@ -87,8 +86,15 @@ export default function transformObject(
       // If we got here, the property hasn't been transformed yet and
       // does not use a value reference. Transform the property now and assign it.
       transformedObj[name] = transformToken(setupProperty, options);
-      // Remove the property path from the deferred transform list
-      pull(deferredPropValueTransforms, pathName);
+
+      // Remove the property path from the deferred transform list, starting from end of array
+      for (let i = deferredPropValueTransforms.length - 1; i >= 0; i--) {
+        if (deferredPropValueTransforms[i] === pathName) {
+          // Important to use .splice and mutate the original array all the way up
+          deferredPropValueTransforms.splice(i, 1);
+        }
+      }
+
       // Add the property path to the transformed list so we don't transform it again.
       transformedPropRefs.push(pathName);
     } else if (isObj) {
@@ -96,7 +102,7 @@ export default function transformObject(
       transformedObj[name] = transformObject(
         objProp,
         options,
-        transformationContext,
+        { transformedPropRefs, deferredPropValueTransforms },
         path,
         transformedObj[name],
       );
diff --git a/lib/transform/token.js b/lib/transform/token.js
index 8d1da2ef3..4a107469e 100644
--- a/lib/transform/token.js
+++ b/lib/transform/token.js
@@ -11,7 +11,6 @@
  * and limitations under the License.
  */
 
-import { clone } from '../utils/es6_.js';
 import usesReference from '../utils/references/usesReference.js';
 
 /**
@@ -23,7 +22,7 @@ import usesReference from '../utils/references/usesReference.js';
  * @returns {Object} - A new property object with transforms applied.
  */
 export default function transformProperty(property, options) {
-  const to_ret = clone(property);
+  const to_ret = structuredClone(property);
   const transforms = options.transforms;
 
   for (let i = 0; i < transforms.length; i++) {
diff --git a/lib/transform/tokenSetup.js b/lib/transform/tokenSetup.js
index 8bf6e6c48..178a43699 100644
--- a/lib/transform/tokenSetup.js
+++ b/lib/transform/tokenSetup.js
@@ -11,8 +11,8 @@
  * and limitations under the License.
  */
 
+import { isPlainObject } from 'is-plain-object';
 import deepExtend from '../utils/deepExtend.js';
-import { isPlainObject, isString, isArray, clone } from '../utils/es6_.js';
 
 /**
  * Takes a token object, a leaf node in a tokens object, and
@@ -27,8 +27,8 @@ import { isPlainObject, isString, isArray, clone } from '../utils/es6_.js';
  */
 export default function tokenSetup(token, name, path) {
   if (!token && !isPlainObject(token)) throw new Error('Property object must be an object');
-  if (!name || !isString(name)) throw new Error('Name must be a string');
-  if (!path || !isArray(path)) throw new Error('Path must be an array');
+  if (!name || !(typeof name === 'string')) throw new Error('Name must be a string');
+  if (!path || !Array.isArray(path)) throw new Error('Path must be an array');
 
   let to_ret = token;
 
@@ -49,7 +49,7 @@ export default function tokenSetup(token, name, path) {
     to_ret.attributes = to_ret.attributes || {};
     // An array of the path down the object tree; we will use it to build readable names
     // like color_font_base
-    to_ret.path = clone(path);
+    to_ret.path = structuredClone(path);
   }
 
   return to_ret;
diff --git a/lib/utils/deepExtend.js b/lib/utils/deepExtend.js
index 174c526e3..bd15ac809 100644
--- a/lib/utils/deepExtend.js
+++ b/lib/utils/deepExtend.js
@@ -11,7 +11,7 @@
  * and limitations under the License.
  */
 
-import { isPlainObject, isArray } from './es6_.js';
+import { isPlainObject } from 'is-plain-object';
 
 /**
  * TODO: see if we can use deepmerge instead of maintaining our own utility
@@ -26,15 +26,7 @@ import { isPlainObject, isArray } from './es6_.js';
 export default function deepExtend(objects, collision, path) {
   if (objects == null) return {};
 
-  var src,
-    copyIsArray,
-    copy,
-    name,
-    options,
-    clone,
-    target = objects[0] || {},
-    i = 1,
-    length = objects.length;
+  let target = objects[0] || {};
 
   path = path || [];
 
@@ -43,33 +35,36 @@ export default function deepExtend(objects, collision, path) {
     target = {};
   }
 
-  for (; i < length; i++) {
+  for (let i = 1; i < objects.length; i++) {
+    const options = objects[i];
     // Only deal with non-null/undefined values
-    if ((options = objects[i]) != null) {
+    if (options != null) {
       // Extend the base object
-      for (name in options) {
+      for (const name in options) {
         // Not everything extends from Object in browser context, so bind from Object just in case
         if (!Object.hasOwnProperty.bind(options)(name)) continue;
         if (name === '__proto__') continue;
 
-        src = target[name];
-        copy = options[name];
+        const src = target[name];
+        const copy = options[name];
 
         // Prevent never-ending loop
         if (target === copy) {
           continue;
         }
 
+        let copyIsArray = Array.isArray(copy);
         // Recurse if we're merging plain objects or arrays
-        if (copy && (isPlainObject(copy) || (copyIsArray = isArray(copy)))) {
+        if (copy && (isPlainObject(copy) || copyIsArray)) {
+          let clone;
           if (copyIsArray) {
             copyIsArray = false;
-            clone = src && isArray(src) ? src : [];
+            clone = src && Array.isArray(src) ? src : [];
           } else {
             clone = src && isPlainObject(src) ? src : {};
           }
 
-          var nextPath = path.slice(0);
+          const nextPath = path.slice(0);
           nextPath.push(name);
 
           // Never move original objects, clone them
diff --git a/lib/utils/es6_.js b/lib/utils/es6_.js
deleted file mode 100644
index f6b6a2bed..000000000
--- a/lib/utils/es6_.js
+++ /dev/null
@@ -1,150 +0,0 @@
-/*
- * Copyright 2017 Amazon.com, Inc. or its affiliates. All Rights Reserved.
- *
- * Licensed under the Apache License, Version 2.0 (the "License"). You may not use this file except in compliance with
- * the License. A copy of the License is located at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * or in the "license" file accompanying this file. This file is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
- * CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions
- * and limitations under the License.
- */
-
-import * as ChangeCase from 'change-case';
-
-export const reduce = function (obj, f, accumulator_init) {
-  return Object.keys(obj || {}).reduce((accumulator, key) => {
-    let value = obj[key];
-    return f(accumulator, value, key, obj);
-  }, accumulator_init);
-};
-
-export const forEach = function (obj, f) {
-  Object.keys(obj || {}).forEach((key) => {
-    let value = obj[key];
-    f(value, key);
-  });
-};
-
-// Note: This is a crappy version to a certain extent... don't use with Strings, for example...
-export const clone = function (object) {
-  return Object.assign(new object.constructor(), object);
-};
-
-export const cloneDeep = function (obj) {
-  if (obj === null || obj === undefined || typeof obj !== 'object') {
-    return obj;
-  }
-
-  if (obj instanceof Array) {
-    return obj.reduce((arr, item, i) => {
-      arr[i] = cloneDeep(item);
-      return arr;
-    }, []);
-  }
-
-  if (obj instanceof Object) {
-    return Object.keys(obj || {}).reduce((cpObj, key) => {
-      cpObj[key] = cloneDeep(obj[key]);
-      return cpObj;
-    }, {});
-  }
-};
-
-export const isObject = function (value) {
-  const type = typeof value;
-  return value != null && (type === 'object' || type === 'function');
-};
-
-export const isString = function (obj) {
-  return typeof obj === 'string' || obj instanceof String;
-};
-
-export const isArray = function (obj) {
-  return Array.isArray(obj);
-};
-
-export const isEmpty = function (obj) {
-  return [Object, Array].includes((obj || {}).constructor) && !Object.entries(obj || {}).length;
-};
-
-export function isPlainObject(value) {
-  if (
-    typeof value !== 'object' ||
-    value === null ||
-    Object.prototype.toString.call(value) !== '[object Object]'
-  ) {
-    return false;
-  }
-  if (Object.getPrototypeOf(value) === null) {
-    return true;
-  }
-  let proto = value;
-  while (Object.getPrototypeOf(proto) !== null) {
-    proto = Object.getPrototypeOf(proto);
-  }
-  return Object.getPrototypeOf(value) === proto;
-}
-
-export const filter = function (arr, filter) {
-  if (typeof filter !== 'function') {
-    throw 'filter is not a function';
-  }
-  if (typeof arr === 'undefined') {
-    return [];
-  }
-  return arr.filter(filter);
-};
-
-export const assign = function () {
-  let args = Array.prototype.slice.call(arguments);
-  args.unshift({});
-  return Object.assign(...args);
-};
-
-export const pull = function (arr, ...removeList) {
-  var removeSet = new Set(removeList);
-  for (let i = arr.length - 1; i >= 0; i--) {
-    if (removeSet.has(arr[i])) {
-      arr.splice(i, 1);
-    }
-  }
-};
-
-export const unique = function (arr) {
-  return [...new Set(arr)];
-};
-
-export const upperFirst = function (str) {
-  return str ? str[0].toUpperCase() + str.substr(1) : '';
-};
-
-const matchFn = function (inputObj, testObj) {
-  if (isObject(testObj)) {
-    return Object.keys(testObj).every((key) => matchFn(inputObj[key], testObj[key]));
-  } else {
-    return inputObj == testObj;
-  }
-};
-
-export const matches = function (matchObj) {
-  let cloneObj = cloneDeep(matchObj);
-  let matchesFn = (inputObj) => matchFn(inputObj, cloneObj);
-  return matchesFn;
-};
-
-const DEFAULT_OPTIONS = {
-  transform: ChangeCase.camelCaseTransformMerge,
-};
-export const changeDefaultCaseTransform = function (caseFunction, default_options) {
-  return (caseToChange, options) =>
-    caseFunction(caseToChange, Object.assign({}, DEFAULT_OPTIONS, default_options, options));
-};
-
-// aliases
-export const each = forEach;
-export const forIn = forEach;
-export const camelCase = changeDefaultCaseTransform(ChangeCase.camelCase);
-export const snakeCase = ChangeCase.snakeCase;
-export const kebabCase = ChangeCase.paramCase;
diff --git a/lib/utils/flattenTokens.js b/lib/utils/flattenTokens.js
index 1cdae2d8b..d7b64d9b2 100644
--- a/lib/utils/flattenTokens.js
+++ b/lib/utils/flattenTokens.js
@@ -11,7 +11,7 @@
  * and limitations under the License.
  */
 
-import { isPlainObject } from './es6_.js';
+import { isPlainObject } from 'is-plain-object';
 
 /**
  * Takes an plain javascript object and will make a flat array of all the leaf nodes.
diff --git a/lib/utils/references/getName.js b/lib/utils/references/getName.js
index 7711421b1..a4b14b7ac 100644
--- a/lib/utils/references/getName.js
+++ b/lib/utils/references/getName.js
@@ -22,8 +22,8 @@ import defaults from './defaults.js';
  * @returns {string} - The paths name
  */
 export default function getName(path, opts = {}) {
-  const options = Object.assign({}, defaults, opts);
-  if (!path || !(path instanceof Array)) {
+  const options = { ...defaults, ...opts };
+  if (!Array.isArray(path)) {
     throw new Error('Getting name for path failed. Path must be an array');
   }
   return path.join(options.separator);
diff --git a/lib/utils/resolveObject.js b/lib/utils/resolveObject.js
index 57d0d9406..e345be12a 100644
--- a/lib/utils/resolveObject.js
+++ b/lib/utils/resolveObject.js
@@ -11,7 +11,6 @@
  * and limitations under the License.
  */
 
-import { cloneDeep } from './es6_.js';
 import GroupMessages from './groupMessages.js';
 import usesReference from './references/usesReference.js';
 import getName from './references/getName.js';
@@ -31,7 +30,7 @@ let updated_object, regex, options;
 export default function resolveObject(object, opts) {
   options = Object.assign({}, defaults, opts);
 
-  updated_object = cloneDeep(object); // This object will be edited
+  updated_object = structuredClone(object); // This object will be edited
 
   regex = createReferenceRegex(options);