I agree, it's arguably clean, and definitely an improvement over Windows 98 era GUI, probably also XP era. But the world has moved on. Even KDE looks better today.
I honestly don't get this, what have we gotten since that's a considerable UI improvement? Bigger paddings? Flat UI?
IIRC you can even configure custom colors, have dark mode, etc. It might look dated with the gray color scheme but that's really the only thing I can guess would look dated to someone.
