I'm not sure I agree. I used the Chicago95 theme (with some added 98 icons) for a good 2 years. The only reason I stopped was because I left the job I was at and couldn't be bothered to replicate the experience on my private device and haven't really been using Linux as my main driver. My team found it hilarious and I thought the theme was quite usable. I find modern Windows windowing far more egregious and unusable. I can't even think of anything you might mean that would justify moving away from the 90s themes or UI concepts.

edit: I've recently been using Chromafiler (https://github.com/vanjac/chromafiler) and I'm realizing we've gone off in completely the wrong direction since the 90s.