So naturally Microsoft decided to completely scrap it, replace it with a far less functioning successor, flop, and then repeat this process over and over til we get where we are today after WPF->UWP->WinUI2->WinUI3. And WinUI3 has also already been completely abandoned. Contrary to this article, it still doesn't even have a visual designer. The amount of time, energy, and money Microsoft has spent with all of these successors is going to be remarkable, just to keep throwing everything away and restarting.
Oh and while all of this was happening they've also been developing Xamarin, MAUI, and more that also all do pretty much the same thing - in completely incompatible ways, with a similar general trend of having the attention span, focus, and overall quality of a 13 year old ADHD boy, in a Japanese arcade, after 7 shots of espresso. This just isn't the sort of thing you could do without just completely absurd budgets and minimal concern about actually making something great. If they had instead just stuck to perpetually refining WPF, UI development on Windows would be a utopia today, and they probably would have saved an immense amount of money, or at least manhours.