I think very generally speaking, you have a point. But there are genuinely changes which make things worse.
For example, in Firefox 89 the contrast between the active tab and the inactive tab is so low that they are not distinguishable when the viewing angle to the screen or the lighting isn't perfect - looks fancy, but is not even acceptable by their accessibility standards.
On top of that they removed the blue bar that - as a crutch - indicated the active tab ?
I don't understand being this invested in such an obiously bad design decision - contrast is just neccessary.
All that being said, I found a bug report from 19 years ago, when Firefox was still called Phoenix, that complained about almost the exact same issue (sans the blue bar), and it got fixed.
I don't think "UX crisis" is neccessarily too strong a word.
I think the problem is everyone on here hates it when stuff they use changes and that’s all.