[druska]

Always writing code will also make you a better developer.

[icecubed]

Becoming a better developer requires a certain level of self-criticism and willingness to improve and learn. Just writing (lots of) code alone will not.

[a3voices]

Writing lots of code will make you a better developer if you lack the experience, but you will plateau if that's all you do.

[peterwwillis]

And delivering pizzas will make you a better driver. But it's not a good career choice.