The new "chunky" layout and UI elements are not really an improvement, and a lot of users have been unhappy with this. Despite plentiful feedback about this during beta testing Mozilla have basically opted to force it through anyway.
UI changes in general are something to expect, but if you're just going to disregard user feedback then you can't claim to respect users.
If that many users are happy why does it keep losing market share?
Personally every other release they remove features I like and make arbitrary UI changes. The only reason I'm still complaining and not using something else is because I don't like the alternatives either.
It's a good way to further push away a chunk of your userbase. They're moving towards a touch-friendly UI, but a lot of us just want a compact desktop app that doesn't waste screen space with excessive padding.
The proper solution to this would be to have different modes if this is so critical. To their credit they did put in a "compact" mode after beta, but this is explicitly "unsupported" and even then still has more padding than "large" mode in the old UI.
Push where? At least you still can configure chrome padding and element sizes with CSS tweaks, unlike the main competitor and its wooden interface with absolutely zero customization possibilities.
There's Vivaldi, and it too uses HTML for its interface, but the team doesn't seem to care about UI performance at all.
The average browser user doesn't know anything about CSS tweaking. Advanced users may know about it if they're curious enough or work with web technologies. People get pushed around by other reasons, mostly things like OS integration (Edge, Chrome).
> There's Vivaldi, and it too uses HTML for its interface, but the team doesn't seem to care about UI performance at all.
Thanks to that, Vivaldi also actively supports CSS tweaks like Firefox. They do indeed care about UI performance and work towards fixing it... The 3.7 update really improved its UI responsiveness. Still, it feels slower than Chrome/Brave/Firefox.
This sounds like a counter-argument. What the Gnome team did (during the 2->3 transition) was a huge overhaul while completely ignoring the habits and wishes of their users. I understand they had to rewrite the old code, that's perfect. I also understand they wanted to "refresh the UI" at the same time. But you can't just change everything and think your users will be happy. If you act against the wishes of your users, who do you write your software for? It simply made no sense and that's why people turned to MATE.
With most things, if you want to completely avoid eventual, inevitable UI changes, you need to just never upgrade.