What are you claiming was improved compared to Win2K? As far as I can remember everything after that was dumbed-down UI and pointless security clickthroughs.

Win+arrow keys for docking to sides I use all the time. Much better multi monitor support. Grouping taskbar. Start menu that lets you search (ie to run notepad, press win then start typing note.. and hit enter)

The search box in the start menu was a huge improvement for me. And AeroSnap to a lesser degree. On MATE, I set Win+arrow keys to do the same thing.

Vista added a lot of usability features like window snapping and start search, but it's underlying OS was literally unfinished. 7 became what Vista, could've been and even Vista became usable when enough updates were applied.

7 disabled a lot of the security prompts for usability. It didn't remove them, it actually just automatically approved them. These days, most software doesn't need admin privileges anymore. You could always turn off all of the prompts if you wanted to, I think there were 4 levels of prompt severity?

Mostly 64-bit by default (going from 4GB to 16GB in 2011 was huge), SSD Trim support and some updated networking protocols.

It's all inside. The wow64, very good management, etc. etc. And Win7 is the last to have the "no desktop compositor" (aka "win95 looks") fallback.