I agree with the choice of Windows 2000. The reaction to Windows XP was that it was too videogamish with its choice of colors and bezels. Then it lasted for so many years past Vista and in part Windows 8 that it became the reference Windows interface. Then the flat UIs mimicking the web and also the 80s with simple elements (we couldn't do complicated widgets back then, not enough pixels.)
Win XP with classic look was pretty decent and useable. There was an option in system settings to disable all theming, 3D stuff, animations etc. just the basic look of that time and a lot more snappy UX.
Do you have a picture of what that looked like? I'm curious. When I search for it, I can only find pictures of normal Windows XP and older versions of Windows. I can only imagine it looking like Windows 95 again.
Also took the good parts from Windows NT. I loved using Windows 2000. I remember being really mad when XP came out and it added all the colourful and curvy GUI elements - felt really dumbed down.
Got an old Dell running Windows 2000. Its remarkable how responsive the UI is. I open an Explorer window, it paints instantly. The Start Menu pops up completely drawn in a fraction of a second.
Windows 11 on a monster machine is sluggish by comparison -- I can feel it drawing each window I open.
I was just having the argument the other that dragging windows on Haiku on a plain old unaccelerated framebuffer just feels an order of magnitude faster than dragging windows around on Windows 11 with all acceleration enabled. On a 5K monitor. Windows is not setting a very high bar these days.