That argument works to an extent, but all of those screenshots are from components of the operating system itself, not third-party apps. Surely Microsoft has the resources to keep the core components of their OS up to date, and if not, they should devote fewer resources to creating new APIs and more to using them.

Deprecating all but one GUI framework doesn't mean breaking all but one. It just means picking one option and adopting it wholeheartedly. How different would all these Microsoft frameworks have been if they were only finalized after gaining the experience of porting over the entire OS? Microsoft might have ended up with a solution that could unify the landscape on its own merits.

Apple's OS X/macOS has always had an evolving look and feel with notable first-party apps that don't conform, but it's never been half as inconsistent as Windows has gotten.

And what I don't understand is that they are capable to create tools to create very productive UI, but do not seem to be using them themselves. Refreshing the appearance of a menu should take one of their intern a day at most.