Mint Mobile does a remarkably good job of defining who they are... and who they are not.
Mint Mobile regularly defines itself as an atypical (read: better) telecommunications provider.
You certainly don't need to define yourself in terms of your competition -- and in many cases, doing so would be unwise -- but considering most people despise their telecommunications providers, positioning Mint Mobile as "not like those other guys" is a pretty solid strategy.
Of course, it's easier to get your message across when your owner is a handsome, hilarious, beloved celebrity and your brand is genuinely irreverent. But that's beside the point.
The point is you won't achieve significant growth if you don't have your fundamentals right.
And knowing who you are, what problem you actually solve for people, why you're better than other alternatives available to your customers, and how to communicate these things to the right people (at the right time, at the right place)...
... those things are fundamental.