I remember in the late 1990s Windows applications, particularly the little weird ones like the app you would use to work a (flatbed) scanner, often tried hard to have unique themed appearances. The industry seemed to lose interest by 2005 or so. I got a job as a Silverlight programmer not long after that which got me to learn WPF and WPF had facilities for theming that seemed capable and well thought out (would be easy, for instance, to turn pill buttons diagonal) but these hardly ever got used, I think the industry had moved on.

Lately I have had to run Office '98 which tries to take over your desktop with Clippy and other things and it still tries to do it to Windows 11. The borderless windows from Office '98 don't quite look right now but it all works.