I'm starting to suspect that general-purpose languages just aren't flexible enough to keep up with changing fashions in UI development. Whenever somebody comes up with a new UI paradigm, you're not going to be able to take full advantage of it until somebody designs a new programming language with that paradigm in mind.
If so, this might explain why the Windows team keeps pushing new desktop UI libraries, only to abandon them within a few years - they just don't have the willingness or resources to migrate away from C# and C++, and so the quality of their UI libraries is stuck in 2006.