I guess I didn't quite convey what I meant. My point there was: if you haven't been using modules to help with common or complicated parts of an app, then you're working too hard by trying to write these parts on your own, and you are probably going to make mistakes that a module author has already taken care of (so your code might not be so good). If instead you were investing time to learn the use of good modules, you would (usually) be able to write better code (and usually take less time overall to finish an app).
It's not that working hard and writing lots of code will be of no use for building skills -- surely practice leads to improvement. It's just that improvement can go much faster when you see how other people solve problems, and you "stand on the shoulders of those who came before you".