Mobile and desktop are two different beasts, and all the effort in the world won't make them equivalent. If you want to hit mobile devices, fine, use Xamarin. If youre building for desktop, use something that makes sense there, like WinForms or WPF. You've got wildly different screen sizes, form factors, and input devices between the two classes of devices, and always will. Cramming them together just gets lowest-common denominator garbage, like UWP.