The teen in me, with a Nokia 6600 besides the computer, was in awe when a single installation of Vista Theme Pack and rebooting a couple times meant that everything on my 40GB HDD Pentium computer was changed from the login screen to icons, wallpaper, fonts, shell, file copy boxes, disk space meter, desktop CPU-o-meter dials to a whole modern look.
I think resolution-independence has made creating themes much more difficult, and not a lot of people are up to the task.
Something like this shows the diversity in themes:
https://macgui.com/downloads/?cat_id=25
Wayback machine link
https://web.archive.org/web/20040404162223fw_/http://www.kal...
“Skins” were popular in the windows ecosystem around XP, but it was far from the peak of customization.
It was most definitely peak customization.
LiteStep is amazingly customizable and versatile, but it doesn't come close to being able to, for example, define pixel shaders in a theme, or being able to easily change any UI element anywhere using simple HTML/CSS, or completely switching paradigms by just changing around a few dotfiles.
Fluxbox itself. Fvwm. Enlightenment. Sawfish.
With fluxbox you had over 1000 themes. And winamp skins worked on xmms.
Also, fvwm was so distinct that you could have tablet like setups before even tablets existed, even with those infamous thumbnail minimizations, but in 2004.
But r/unixporn disagrees about peak amount of customization.
XP theme customizations wasn't even close to what you could do on Unix at the time.
Only if you consider computing is limited to Windows/Mac.