What is the alternative then? How would you have created a new Windows desktop application in 2015? 2018?

And yes, since 2012 there were no major changes to WPF. And even these changes were small. The last truly major change came with .NET 4.0. So there was a decade of almost nothing, even while XAML evolved with UWP. It truly doesn't get any more dead than that.

Of course I'm salty. WPF promised a lot, delivered some then died. Xamarin wasn't even part of Microsoft back then. UWP is a joke. Microsoft neglected the "Win32" desktop for way too long. Now it lets the community do what it should've done ages ago.