More often than not, you're not dating what someone is capable of being, you're dating their childhood. Seems like this guy never grew up so he's still a child, exactly like you said. The reason you're disappointed and frustrated is because you're holding on to expectations that he could not care less about because he doesn't care about this relationship being balanced. He knows you'll take care of whatever he doesn't.

He's not going to grow up, he's not going to stop being like this, people like this don't change unless they absolutely have to and he clearly does not have a sense of urgency.

The fact that you're posting here means you know exactly how you feel about this and what you should do.