What Firefox 78-80 brought was hardware video decoding under Linux, not hardware video decoding in general.

Under Windows and MacOS, it has been implemented years ago. Under Linux, it wasn't. Linux has API for video acceleration and players like VLC, mpv or Kodi have been supporting it for years, as well as ffmpeg, just browsers ignored it.

I'm not going to belittle the effort, quite opposite, but it is telling when this feature has been implemented by Redhat employee and not Mozilla.

Should have been, after all Flash was doing it 10 years ago.

Since Flash plugins were killed, Linux has been a mess for hardware accelerated video on the Web.

Not killing gstreamer way back when would've helped.