Interestingly enough, in practice, there are various declarative SwiftUI-style nuget packages for Avalonia[0][1][2] and Uno[3]. You don't actually have to touch XML if you don't want to.

Edit: as someone else noted, the website itself links to a built-in option to do so as well - https://platform.uno/c-markup/

[0] https://github.com/AvaloniaUI/Avalonia.Markup.Declarative

[1] https://github.com/wieslawsoltes/NXUI

[2] (F#) https://github.com/fsprojects/Avalonia.FuncUI

[3] https://github.com/VincentH-Net/CSharpForMarkup

Plenty of folks that criticise XML, have no issues dealing with JSON and YAML spaghetti, ironically.

I agree. It's just quite a lot of verbose-looking XML. "I have to write that much XML" is probably not the first impression you want to give. I did scroll down and see that you don't actually have to write such XML by hand, but many will not.

Good feedback. C# and XAML are on parity. But if you are seeing too much of one and not the other, it needs to be adjusted