When this happens it's often because a backend component gets rewritten and somebody decides that it's too much work to re-implement some features for the new backend. It's much easier to come up with a PR spiel for why removing the features is actually a good thing.
TIL. The wikipedia article with some more detail.
On Android it's the only reasonable choice so no question there.
On desktop I used Netscape/Phoenix/Firebird/Firefox/Conkeror for many years but switched to Chromium when I had to start over after the XUL-apocalypse. But lately I've been maintaining my Firefox setup more or less in parallel with Chromium and this week as it happens I am trying to make the switch back again. Mostly just to wean off the Google stuff. Will see how it goes.
Another (less-critical) motivation is that Chromium takes over 10 hours to build on my machine. Firefox is under 1 and it gets done way faster even if an LLVM or Rust build is involved too.
I've give up on the Youtube homepage long time ago. Only the Subscriptions view (with shorts filtered using a userscript) and search results are usable for me.
x86 Macs are not the greatest example of longevity at this point.
EXWM. I am a longtime Emacs user so merging the concepts of Emacs buffers and X windows is a huge benefit. Only one set of keybindings to worry about, all of my Emacs window management stuff works for X windows too. One less external dependency to worry about too. In a new environment (like when starting a new job etc) as long as I have my Emacs config I am good to go.