> if you wrote a Windows Desktop app in the last 30 years, the only way it would still be supported today ... is if it was based directly on the old Win32 API

I thought the same and did just that to see if it holds true: https://github.com/sjmulder/netwake

By default you get Windows 95 styling and Windows 3 fonts. You have to opt into 'visual styles' (introduced in XP) with a declaration in the app manifest and have to manually query and use the system font. DPI awareness is also opt in and puts all the work (sizing/positioning, scaling/reloading fonts) on you. But when you do that, it does look fine on Windows 10.

Not so much on Windows 11. Some of the widgets have been updated to mimic the new style but when you put it together it looks messy and old fashioned (e.g. fonts + you don't get the new context menus).

I'm curious to learn how one would create a 'proper' Windows app without having to reimplement the system's widget styling.