XAML is good. It's very easy to build interface by nesting components then styling it if needed, and doing data binding. All the web alternatives are harder to use and came 10-20 years later.
XAML is the only thing I was ever able to write a complex layout in, run the app, and see it look exactly as what I intended on the first attempt. That would meet my definition of productivity.
For example, my experience with CSS has been the opposite of that. F5 a million times before the layout works the way I want it to. Sometimes even googling how to do create some type of layout because I can't think of it on my own.
