I was part of the PC demoscene in that era (1997-2002) and it definitely was a super productive and exciting time. The transition to Windows wasn't necessarily a big deal, but the impact of 3d acceleration definitely was.

In that period 3d accelerators were basically capable of running Quake and not much else. Traditional demo effects that relied on reading the backbuffer (even to just do some basic postprocessing) were either unavailable or had to have bespoke implementations per card. There were no shaders to speak of, and so on.

For me that really killed demoscene innovation for a while, and a lot of demos basically consisted of a bunch of alpha-blended layers for a while.

Nowadays, though, I'd say the scene is probably doing pretty well even though it's arguably even more niche than it used to be. Oh well.