Wait a sec. Windows 2000 was probably their best operating system. Windows ME was absolutely their worst. They were so different I’m not sure the entire company wasn’t swapped into the set of Severance (tv show) or something of that ilk.
As an aside - as someone who used ME back in the day, I feel like I honestly had more problems with Vista. ME was a downgrade from 98SE for sure, but I don't remember it being the same level of performance and reliability degradation that I saw going from XP to Vista pre-SP2.
My ME machine would reliably BSOD when I opened / closed the CD tray.
IIRC ME would just randomly crash explorer.exe with task bar disappearing but you could recover some of it. On Vista it was just overall sluggish and laggy visual experience.
Millennium _was_ Windows ME, millennium edition. Windows 2000 was completely different. :)
I did later run Windows 98 on my kids' machine for games, but I never tried, or wanted to try Windows ME.
Windows 2000 has the best look and feel for the GUI, but I do recall that I usually saw my first Explorer crash within an hour of a fresh install. Windows 7 was peak Windows because you could still get the "Classic" Windows 2000 theme, but with all the under-the-hood improvements. I've gotten used to the Windows 10/11 UI, but I've never liked it and just wish I could go back to the way it looked when Microsoft cared about usability, as opposed to trying to make everything look like a phone.