I guess one challenge with this is that old school Win32 doesn't really support anything resembling automatic / responsive layout. All controls are of a fixed size in a fixed pixel location. This means you can't for example change the default font, add margin or padding or do any other significant changes without essentially breaking all existing applications.
That's not quite true. Win32 apps that use CreateDialog use absolute positioning for widgets, but the "dialog units" used for that purpose are specifically defined to scale with DPI and font size (one DU is defined as "average width and height of characters in the system font").
