I'm under the impression, in Udacity's case especially, that part of the problem stems from asking native engineers to use a language and ecosystem that they're not used to working with, and then trying to get them to integrate RN code into an established, brownfield native codebase.
As a sole dev in a 3-person startup, I’ve managed to build a pretty large app with React Native, having zero prior native experience (although, that’s not to say that I haven’t had to learn a _lot_ about Xcode!)
As a sole dev in a 3-person startup, I’ve managed to build a pretty large app with React Native, having zero prior native experience (although, that’s not to say that I haven’t had to learn a _lot_ about Xcode!)