People like what they like, you don't have to justify why. I hate carrots. Why? Doesn't matter, it's still a valid choice, same as start menus.
Before that, the Office 95 applications had a curiously black-to-dark-blue custom drawn title bar.
Then Windows 2000 introduced the subtle mouse pointer shadow, and translucent fade-on-click effect on menu items.
Agree with you about Tahoma being pixel perfect, at 8 point I think. Then came the marvels of ClearType!
As far as translucency - Win2K introduced the new APIs that any app could use to make a window translucent. That was used for those fade-on-click effects, and also for tooltips. But after people figured out that you could do it on any top-level window, there was a brief craze where random apps added it as an option, sometimes for no reason at all other than showing off (like, why would a CD burning app need a translucent window?).
Ironically, you used to be able to run KDE1 in 8 bits per pixel color mode (256-color palette - quite important for performance back then) and that did support titlebar gradients, unlike Win98 in the same hardware mode. That gradient was far from "smooth" of course, but like its Windows equivalent, it was still very helpful in making it easier to spot the titlebar at a glance.
IMHO it was the pinnacle of 2D UI design. Clickable areas were visually obvious, and there was no ambiguity about what happened and why.
And now we live in a world where fashion rules over function.
And didn't NeXTSTEP built on Motif in turn? Is Motif the granddaddy of "chiseled 2D", or was there something before it?
[1]: https://i.imgur.com/gpJbTLl.jpg
[2]: https://i.imgur.com/lpKrYe0.jpg
Majority of powerusers despised default Luna and often used Classic theme instead; Watercolor had a potential of being Classic v2 with its 9x simplicity and modern (as for those days) touch, sadly it wasn't included by default.
IMO, the timeless Windows look is Win2K - it's when they got the original Win95 / WinNT4 look perfect. They adjusted the colors a little bit so it was less dark, and IIRC that was also the first version to have sky blue wallpaper background by default, and blue gradient title bars. It was also the first to switch from MS Sans Serif to Tahoma 8pt for the UI font, and Tahoma was pretty much pixel perfect at that size.
So the overall effect was that it looked more cheerful than Win9x, but not cartoonish.
https://i.imgur.com/jwzJiSW.png