If I recall correctly, Win2K was a lot slower than NT 4.0 on the same hardware, and it featured some really bad UI ideas, like menus that auto-hide advanced menu items.
By the time XP was released I gave up the fight.
The initial XP theme was just awful; clearly a knee-jerk reaction to the OS X Aqua. It's too bad. The MS Whistler prototype screenshots looked great.
https://guidebookgallery.org/screenshots/whistler2257
The later XP theme (Powerpack?) was half decent.