Also, the relationship between UWP XAML and WPF XAML is a lot closer than (for example) Win16 versus Win32 or MFC versus WinForms. Even if WPF is "just in maintenance mode", UWP is seeing active development. Some of UWP XAML additions have even back-ported to WPF, and "XAML Islands" even mean support for putting UWP XAML directly inside WPF XAML.