Weirdly enough, this tends to be where Apple's docs are still good. They fall apart when you try to move on from it towards Swift & co.
Granted, _finding_ the ObjC old docs can be a pain in the ass, but it's possible. I've literally found answers to some of my questions in OS release notes and nowhere else; part of being an AppKit/etc developer winds up being simply knowing how to search.
Another complaint I have: depending on what era of documentation you need, you often have to qualify your searches differently - e.g, OS X vs macOS.
Granted, _finding_ the ObjC old docs can be a pain in the ass, but it's possible. I've literally found answers to some of my questions in OS release notes and nowhere else; part of being an AppKit/etc developer winds up being simply knowing how to search.
Another complaint I have: depending on what era of documentation you need, you often have to qualify your searches differently - e.g, OS X vs macOS.