More moving parts when something goes wrong, which it will. You don't have to specify that you're using "macOS Ventura with the Glendale desktop environment and Hwy 101 window server" or something. Win2000 help might even be relevant in Win10 cause they prioritized familiarity.

Even at my job where gurus are managing our workstations full-time, Linux users randomly had to all switch desktop environments cause of X dependency getting too old, and the new one partially broke compatibility with our remote desktop. It's not a perfectly layered cake.

I also don't believe that people's use cases are really so different that there need to be so multiple widely-used Linux DEs. I'd get it if there were GNOME for almost everyone then other niche DEs for the rest. Again, so many people with a variety of use cases have managed ok with the basically unchanging Windows UI for decades.