Earlier quoted context omitted.
As strange as Snapchat's UI is versus the standard mobile OS's UI guidelines, there's no denying their unorthodox UI has been wildly successful. There's definitely things to learn from their strategy.
I don't think it has been successful for on-boarding new users. They are overwhelmed and don't know how to use the app.
Personally, I don't buy it. Snapchat still manages to onboard new users who eventually learn how to use the app despite all its shortcomings, because people really want to use Snapchat. Having 'good UX' is just a shortcut for having people inside your app who aren't as committed to it.