> no add on support (even for those add-ons who had an an FF product)

Assuming we’re talking about Android here, what do you mean by this? Mobile Chrome has no extensions, whereas Firefox supports the full suite of desktop addons. I can use uMatrix and even developer extensions on my phone with Firefox.

Also, I think the point of the “videos creating notifications” thing is so that you can continue listening to the audio after turning off your phone, like on iOS and iPadOS. Apple got the battery thing better in general. Maybe Firefox should stop playing videos in the background after a certain period without user intervention?

Some of the other things can be chalked up to bugs (it would be nice of you to submit something to their Bugzilla!), while some I have never seen myself (especially the videos thing... for me they’ve always played in window, with the bottom UI, correctly; it could be a problem with your favorite video site?)