I literally googled a few hours ago for "Why is Apple documentation so shit?" I mean, look at SwiftUI. Conceptually it's great, but it is also fucking buggy as hell, and I think one of the main reasons is that the developers themselves don't have good documentation available. The best documentation so far I found is this, but it's third-party: https://www.objc.io/books/thinking-in-swiftui/
SwiftUI is not great in any sense, other than looking great to people who've never written non-trivial software. When your criteria for 'great' is whatever 'content creators', 'software journalists' (email newsletter 'creators') and apple's marketing team pump out this week, 'great' is anything a marketing firm puts dollars behind that seems 'cool' and 'fresh' and 'hip', or is it 'dope' this week? It is quintessentia…
SwiftUI brings concepts from React and Flutter to the Apple ecosystem, which is great. It's especially great for people writing non-trivial software, because we don't want to spend our time on doing trivial stuff.