The lack of the one cross platform UI framework to rule them all can be a downside, as has Microsoft's adventures with creating and abandoning modern UI frameworks. But on the flip side this has led to a proliferation of third party options.
Avalonia works everywhere, and they recently made MAUI run on top of Avalonia to give it Linux and WebASM support. They also have a commercial product to run WPF cross platform using Avalonia. So not only do they provide a good option, they have made two of Microsoft's frameworks work cross platform as well.
Then there is Uno Platform, which is basically a cross platform WinUI implementation. There is also Eto.Forms if you want a simple desktop focused toolkit that wraps the native platform's widgets. There are also a lot of ways to bring Blazor to native applications. You can even use QT with QML.NET, though that isn't actively maintained.
It was simpler to choose a UI for C# in the early days. All you had was WinForms. Then for a while you had Winforms or WPF. Now this decade there is a pile of options.