Indeed, that is why Microsoft has created teams to support React Native for macOS and Windows, on Windows case it makes use of UWP, which new roadmap (WinUI 3.0) was announced at BUILD 2019, with more details to come up on Ignite.
Given the market size of laptops, 2-1 hybrids and graphical workstations running Windows, the UI/UX toolings that are available, I fail to see what you mean.
I mean the experience of using Windows has dramatically declined in the past 5 years. Forced Windows updates was a terrible idea, updates break things much more often, the start menu has ads in it by default, start menu search does strange things, it's possible to break the start menu, if you unpin an application from the task bar while it has running instances and then re-pin it you'll sometimes end up with multiple icons, the new settings panels are slower and less capable than the old ones...
Yeah, Microsoft bashing never grows old.