Why GCM/FCM support without VAPID keys is removed?

[omitech]

Why GCM support has been removed? I think it is still possible to send web pushed to FCM endpoint with Authorization: key= header without VAPID

[lukewarlow]

As far as I'm aware Chrome was the only browser to support it and this issue https://bugs.chromium.org/p/chromium/issues/detail?id=979235 shows it's been deprecated.

[Tikolu]

I've been struggling with this issue for a couple of hours now. Is there any way to send a push notification to an FCM endpoint using this library?
I keep receiving the authorization header must be specified error.

EDIT: Here is my own issue on the topic #325

EDIT 2: Turns out I was entering my security keys incorrectly, more details here: #325