My claim is that firefox gets worse by adding the features nobody asked for

Most of those new features are absolutely amazing, like the instant translation of almost any page,
Creating tags for images that don’t have them for blind people, is an amazing feature for blind people.
If you don’t like them you don’t have to use them. You don’t get to dictate that others shouldn’t have them on false accusations.
Some of us like a feature-full high quality browser, that respect our privacy.

purely out of FOMO of the AI hypetrain

OK and which functions are that?
You’re just on the AI hate train and think that’s the default correct position.
Well guess again, because Mozilla is actually using it for things that are both useful and noninvasive.
So why don’t you piss off and go use a terminal browser instead if that’s what you want.
Alternatively there are a lot of decent open source browsers that don’t have the advanced features of Firefox you can use.