To me personally, it feels like Windows 2000 was the last and maybe only consistent UI onto which all later versions bolted what they considered improvements without ever overhauling the UI in full.
Moreover, Windows XP let you switch the interface back to the classic 9x look, if you wanted a more serious appearance, and better performance.
If i remember correctly this is the windows 2000 look.
Although I‘m a Mac user for a long time, I still remember that I got work done using Windows 2000.
I‘d buy a license and switch back to Windows if we could get the productivity of this UI.
Typing this on iOS with Liquid Glass that drives me nuts