Same here, Windows 2000 is peak UI, I never liked the Frutiger Aero aesthetics. My only criticism is that it was, in a sense, too successful and elements like the taskbar and start menu got ossified and the design stagnated. Apple's F3 show all windows, F4 spotlight is far better. Windows didn't even get multiple desktops until Windows 10.
I guess I like the design language but I wouldn't be prepared to give back the usability of modern UIs.
Frutiger Aero was never called like that. It was just a non-copycat gloss theme cleraly inspired from OSX' Aqua design. Even KDE3 did that for some time (Everaldo/Crystal icons, Keramik...) were rounded, glossy designs were hip and transparencies with XRender were everywere.
Both desktops tried to create someting shiny without being too close to Mac OS X.
TBH KDE has better themes like the Slick icon set and plain but contrasted widget and menu themes, kinda like the semi-flat theme from Office 2003 (was it the .Net theme?) or something like that, which was modern but not baroque and overloaded like Keramik or XP's silver theme with too many gradients.
That style would modernized would be several times than the unusable flat themes from today. Kinda like Zukitre for GTK2/3/4 under GNU/Linux and BSD desktops (ad QT5/6 being set to match the GTK3/4 themes under the settings).
Windows didn't even get multiple desktops until Windows 10.
I believe that it has always supported multiple desktops since the introduction of the NT kernel. There just wasn't any UI provided in the OS for switching. I used a Microsoft PowerToy to switch between desktops, I think all the way back to NT 4.0.