> CRUD apps are non-trivial.

Aren't these pretty much the most trivial UI apps possible? E.g. compared to other native apps like Photoshop, Blender, Visual Studio or Office, CRUD is mostly just about banging together custom UI frontend for a database.

Unity's editor is implemented in its own (old) UI system, same with Godot, so in both engines it's possible to create 'traditional' non-game UI applications.