Calling that "constant churn" is a massive exaggeration. First, using WTL or WFC were just bad decisions because those were side-projects and MS never told companies to switch to that and definitely didn't encourage rewrites into that. They were not replacements of anything by any stretch of imagination. That's like complaining that MS made you rewrite your app in Lightswitch or IronPython. It is just a side-project, not something ever intended to become the main MS dev stack.

So realistically for most MS stack devs it was MFC -> VB -> WinForms -> WPF -> Metro -> UWP. And MFC was released 25 years ago. So they switched 5 times in 25 years. You could possibly add Silverlight in there (which is extremely similar to WPF so only half-counts for churn purposes).

Now, I agree that the Metro -> UWP part was unnecessary because they were doing the same thing twice so they should have gotten it right the first time (and I think the whole UWP concept is worthless anyway).

If we look at MFC -> VB -> WinForms -> WPF, all those technologies provided a lot of value to us and it was very useful to have them. Would you want to still be programming in MFC today? I am pretty sure you wouldn't. I do not feel any "churn" from this (note: I never switched to Metro/UWP because I considered it a step backwards, unlike the previous "switches", so I stopped at WPF when it comes to desktop), I can barely remember programming in VB 6.0 because it was such a long time ago.

Saying that's "exactly the same" as the situation with web is ridiculous.

Your 5 times in 25 years suggests an overhaul every 5 years. Context matters. WPF became mainstream in 2007

WPF, Metra, UWP, and Silverlight in 2007 -> 2017 is 4 overhauls in 10 years or an overhaul every 2.5 years.

Also not fixing bugs in earlier tech creates a compulsion to switch to the next tech.

metro/winrt -> uwp wasn't really an overhaul, it was just a new name for the next version of the same thing more or less.