Win32‘s continued popularity (vs UWP) I’m sure has at least partially to do with how it’s all plain C, which makes it simple to support with any programming language imaginable via bindings. If they were serious about pushing UWP adoption they should’ve provided plain C bindings for it so it could be used with Rust or Python or Swift or whatever. C# and C++ aren’t everybody’s cup of tea.
C++: https://docs.microsoft.com/en-us/windows/uwp/cpp-and-winrt-a... Rust: https://crates.io/crates/winrt C: https://stackoverflow.com/questions/7436144/using-winrt-from...
etc.