I feel like there is some lost perspective here.
> But breaking font rendering?
I would instead see at is making font rendering work equally across platforms.
> Making scrolling work worse?
Again, making scrolling work equally across platforms.
> Not having some generic cosmetic effects like background transparency?
Again, equally.
I am more than a little surprised that this is so surprising to people...it seems rather par for the course for GNU philosophy.
If you truly want to make a platform agnostic piece of software, then you end up limiting yourself to the "lowest common denominator".
People seem to have gotten used to the presumption that if you want to make software, you have to make platform specific versions for the best user experience. Want to write a mobile application? Well the best user experience comes from "native" apps...so you should make one specifically for iOS and then one specifically for Android.
That. Is. A. Huge. Problem. (*at least in the eyes of GNU)
And in principle I agree most of the time. Locked/incentivized eco-systems lead to the dominance of a few "popular" platforms as choosing which platforms to support (as a developer) becomes a function of market coverage. This has been demonstrated time and time again for better and for worse...although usually the latter.
So yes, GNU can be kind of extreme into their adherence to their core philosophies...but, honestly, I don't think this is a "fight" (so-to-speak) that can be made with half measures and exceptions.