You talk like that is a bad thing. Win32 UI works, is fast, works everywhere even on ancient 640x480 server screens, safe mode and vnc in 16 colors without opengl, directx, Angle or vulkan.

Flutter is nicer to scale and maybe design but it is a massive overhead. Skia still has trouble with some drivers and causes lag or falls back to software rasterization. Hot replacement while coding is pretty neat though. It runs much better on mobile devices imho.

It works, and fast, but it is not portable. I would argue something like Qt is much more viable in $current_year for cross-platform development. Or if you're really dead-set on actual native components, then I guess wxWidgets works too.