That's tooling, not Dotnet Core itself. As an aside, I think there is even a WinForms GUI editor in Jetbrains Rider now.
> Marketing and reality are just too far apart
I mean, that's your opinion, but there are millions of Dotnet Core devs for whom the reality is as wonderful as promised. If you still have to work with legacy libraries or maybe WinForms, then of course I understand where you are coming from, but I don't think it's fair to tar the whole of Dotnet Core based on some limited failings that affect only a minority.