How well does it scale in complexity though? These easy declarative UIs tend to have a hard ceiling in complexity and then you're forced to rewrite everything. How does SwitftUI scale to complex and animation heavy UIs?

I haven’t gone too far down the rabbit hole yet but I find it similar to React in complexity ceiling. I’ve built some extremely complicated UIs in React. You just have to break up your views as complexity grows.

Animation is very well thought out, and quite easy.

As for complexity, you hit the ceiling very fast, and the solution is to break up in smaller and smaller custom views and modifiers.