This is the double edged sword that is Rails. It gives you enough to quickly deploy a basic SaaS app and lull you into the false sense of security (it's so easy to launch an app!).

Rushing through learning RoR and not a) learning Ruby and b) actually taking your time to write some tests goes against what is arguably the best practice for learning RoR properly.

Throwing together one app is a start down a path to learning RoR, it's not actually "learning Ruby on Rails". They are two different things.