Many here point out, and rightly so, what an abominable mess UI frameworks have been on Windows for quite a while.

That being said, I'd point out that the situation has been (and still is) unfortunately far from satisfying on the cross-platform and open-source side as well: GTK has also been a mess for quite long; Qt has - aside from the bloat - an increasingly repulsive licensing model for professional use (too bad the hopes from the early Nokia adoption days got smashed by MS mole Elop and the later owners of Qt), …

… and while there are some nice solutions for specific niches (e.g. Dear Imgui), the overall situation in general-purpose cross-platform native UI frameworks looks quite bleak and unsatisfying imho. There's a huge gaping opening for a permissive-licensed open-source cross-platform UI/Widgets framework that compiles to native, has a good set of widgets and gives access to Vulkan contexts for 3D rendering.