I played around in Windows 2000 for the first time in 20 years. I know nostalgia can be blinding, but I would go back to that UI in a heartbeat. The uncluttered taskbar, the simple start menu that isn't full of useless recommendations and ads—such a joy!
I don't remotely want to use Windows 2000 again, but it is interesting to see a version of Windows where the UI was consistent. Currently it is a mishmash of four generations of GUI toolkits, some UI is in one style, some UI is another, etc, etc