Same as the AI integrations. There's obviously a market for them so FF has done some fairly sensible work to add them. And then people here explode like Mozilla has kicked their puppy.
But in all seriousness, it seems to me that firefox has relatively more opinionated users, or users who are very specific/strict about their setup and what they want, and many are often fast and vocal in expressing opinions compared to the other browsers. I don't think we see posts around with people complaining about features in other major browsers in the same way (of course I could just miss them because I would pay less attention to other browsers).
I am pretty sure somebody must have complained about the ff quantum update too, back in the days.
You're right, a bunch of extensions weren't working initially, large parts of the community were upset about that. Eventually, as more extensions were supported and new alternatives emerged, it eventually died out and was almost completely forgotten about, until you reminded me of it just now.
Honestly, I'm still sad about that. It caused a hit to the usability and functionality of Firefox. Some of that has since been compensated for, but parity has not yet been achieved and probably never will.
But even with the functionality reduction, Firefox is still better than the alternatives for me, so I continue to use it regardless. Perhaps, eventually, something better will come along.