i hate how it falls on the user to find and develop workarounds to keep older machines usable today simply because of unnecessary changes, such as proton on firefox taking more tab space on the screen than it needs. this is understandable in commercial software, but...
one of my favourites is how mozilla showcased a new color picker for firefox mobile back in 2013, finally letting us pick any value instead of being limited to a random preset selection that serves nobody. that functionality has yet to come, 8 years later. https://blog.mozilla.org/ux/2013/12/a-new-colour-picker-on-firefox-for-android/
... open source environments like linux have no excuse for it. and i'm not talking about changes that DO need to happen, such as no longer supporting 386 processors. i'm talking about the stuff that could be avoided or made opt-in.