I wouldn't say "completely fucked", but for a few years I noticed YouTube on Firefox has this occasional quirk where videos will quit playing and infinitely buffer at the exact same timestamp. Like there's no way around it except skipping about 30 seconds ahead with the seek bar, or doing a Ctrl-F5 (hard refresh) and starting the whole video over. Opera GX doesn't seem to have this problem at all.

But it's still not a big enough deal to make me give up Firefox completely.