Earlier quoted context omitted.
Except that's not what Microsoft does at all. The .NET Framework is forward compatible and very rarely breaks compatibility. You can select multiple compilation targets for .NET and have a single piece of code that compiles to multiple frameoworks concurrently. I currently am maintaining a handful of Projects that build Nuget packages compatible with .NET Core, .NET Standard and .NET Framework. If you do have compati…
We aren't talking about .NET in general bit about desktop UI frameworks. If you started with ASP.NET MVC years ago you still are on the main platform that's in full development. With desktop development you have several frameworks that are either in support mode or not fully featured.
If you're referring to Silverlight, that was never a serious desktop UI framework. It was initially targeted as a Flash /Java killer but pivoted to cross platform desktop apps when it became clear that it would never be adopted on Mobile and that Apple/Google were actively trying to kill Flash on the desktop.
That being said, we got XAML from Silverlight and it's not terribly difficult to covert ti a XAML or even UWP app from a Silverlight codebase.