I'm a bit late to answer but... I've used a bit of XAML and it is not at all what I have in mind. XAML, SwiftUI and QML all have the same problem, in that they

I'm a bit late to answer but... I've used a bit of XAML and it is not at all what I have in mind. XAML, SwiftUI and QML all have the same problem, in that they mix structure and presentation. A typical XAML app is not easily themeable. Let alone having the ability to adapt to different UI paradigms or toolkits. A symptom is that you have tags like "Rectangle" and attributes like "Margin". The high-level description shouldn't say anything about presentation, just what you want to accomplish. The building blocks should be like "CRUD Editor" or "List-Detail view".