I've run variants of this: https://b00merang.weebly.com/desktop-themes.html on GNOME for quite some time, without putting in the effort to recreate the start menu. My coworkers definitely looked at me weird for my Windows XP theme but it felt very nostalgic. Small details are off, though, unless you go in manually and tweak the CSS even further to correct for the differences between the author's DE and yours.
For LXDE, this project: https://github.com/grassmunk/Chicago95 goes further than just a theme, restyling some common utilities as well. It's not Windows 95, but if you'd told me it was designed around that time I would've believed you.
This post: https://www.reddit.com/r/unixporn/comments/tijkr3/plasma_wel... shows a very good KDE Plasma theme. Some icons are Win98, though, so you may need to replace those for the authentic look and feel.
What I myself would love is for someone to make a proper Windows 7 Aero theme for Linux. The icon sets and the backwards compatibility themes are available everywhere, but there's no Aero theme that's not jarring. In a perfect world, I'd like the frosted glass effect as well, but that's probably too much to ask. I've thrown some Windows DLLs into Ghidra to try and find the frosted glass theme engine code, but I had no idea where to look and couldn't find anything.
Is there a Gnome or KDE theme or clone inspired by Windows 2000? Windows 8, 10, and 11 are simply offensive in comparison. I kept and open mind but still haven't come around to liking any version, not even close to W2K.
Also the BMW 7-series from 1998-1999 was one of the best ever. Every subsequent one isn't nearly as good, IMO.