For a brief, a very brief moment, between beige Windows 98 and glass-like Windows Vista, we had a "fun" Windows XP. Thinking back it's a bit ironic. For most of history the OS'es didn't look fun, but it was that colorful one I'm most fond of.
Where I drew the line was Win8: it started to get really hard to actually accomplish tasks in the OS. Win10 walked that back a bit, enough to be tolerable, then Win11 went the other way. I set up a Win11 desktop last week for the first time: what an exercise in unnecessary pain. (And Windows Spotlight backgrounds, one of the few recent MS shove-down-your-throat features that I actually like, doesn't even work reliably and there's no way to find out why. Absolutely no way. Despite an OS with a comprehensive logging system!)
So it's really not correlated with the skin: it's about the functional bones of the UI. A gaming machine needs a functional UI. (Just like everything else!) But the skin on top of that can, and probably should, have some visual distinctiveness and flair. A spinning cube, though... perhaps that is just a little bit too twee?