As with many things, I think from a pure UI perspective every Windows/Office release made things worse. Win95 was pretty solid, even improved on a few things that they took from the state of art at that time (Nextstep, Classic Mac, OS/2). The Taskbar being a good example.
I'm still not sure that the move from actual buttons on a button bar to just a flat series of icons was right, and many such changes happened after that (culminating in the horror of the ribbon bar).
The big items Win2K/XP brought to the market was stability outside of the NT niche (I really enjoyed NT4). On the UI level, the downgrade continued, especially with that ugly blue standard theme and the bisque semi-rounded UI elements.
But boy, would I like to see some "distro"-fication of that. And I'm not talking about just using different themes or "shell" replacements, but about putting the core parts to good use. It could be amazing to what some dedicated minds could do with COM, OLE, VCL and VBS. A much more modular environment, similar to what OpenDoc promised and didn't keep. (And maybe add some Amiga stuff)
Not that my hopes are very high in that regard, as Linux and the BSDs didn't manage to do that either, despite having most of the technology and even doing some half-hearted attempts (CORBA was a part of early GNOME)…
A Windows shop these days isn't that much different from any other enterprisey shop. Cloud, VM language, web UIs with enough whitespace to hide Moby Dick. Not that many of the smaller shops around that did custom desktop apps for small businesses.
Oh, and as a final note: If you like the aestheticof 90s-ish Win, check out Serenity OS[1]. It's pretty awesome what they put together. A not slavishly POSIX-ish system with a Win95-like UI. Even the starts of a remarkably capable browser…
[1]: http://serenityos.org/