It only took me a few weeks to get caught up and be a proficient iOS developer, but it takes several months to know all the pods, architecture design patterns, tooling and gotchas to be able to lead a team and avoid months of mistakes and rewrites. The official APIs are a small part of it.

Agreed to some extent. You still need some expertise as a general software developer in order to write performant, stable apps, but it's certainly a lot easier to go from zero iOS knowledge to a fully working app than it was 5 years ago.