I agree. Win2k Pro was the best OS Microsoft ever made.
I agree that Win2K's user interface was the high-point -- ever since then, the first thing I have to do with XP or 7 is revert the UI to "Windows Classic" (i.e. Win2K) and tweak some things so it works more like Win2K. Classic Shell helps with 8 and 10 but they're mostly irredeemable.
The underlying OS (kernel, libraries, syscalls) has in fact improved substantially since Win2K. Win2K would be horribly insecure for daily internet usage.
A hybrid of Win2K UI over the Win7 OS foundation would be my goal.
(I almost said "Win2K UI over the Win10 OS foundation" because 10 is more secure than 7, but all the crap and alleged spyware makes me reject that.)
All of which is why I consider Win7 to be the "best OS Microsoft ever made", because I can, in fact, revert enough of the UI back to Win2K mode, to make it almost indistinguishable. Best of both worlds, IMO.