If you stay in the happy path, it's decent, better than it used to be. Microsoft does seem committed to it, they're slowly converting Windows apps to WinUI 3.

That said, the team is clearly understaffed; there are long-standing unresolved bugs, just search for "memory leak" on their GitHub issue tracker. Also, native, non-.NET support is definitely an afterthought, it's barely documented and the tooling is super awkward. But at least, unlike WPF, it exists.