It's the same issue as games. No one ever says "I bought this game becsuse of its clean UI". Not unless you're a dev doing market studies. But at the same time, a bad UI in many genres can sink a game. So UIs tend to be as minimal as necessary to ship. Even Steam had the same UI for some 15+ years beffoe finally giving it different library views

The minimal here was to take the Unreal Launcher (which was always meh. But devs rarely interact with the launcher) and shove the tab into there. Any problems with that launcher were passed to the EGS, and amplified by being B2C.

If I have to be honest, it's also tribalism. Exclusives are not a new concept even on PC. But the reaction to some EGS exclusives was so extreme. The PR hit didn't do many favors.