The game isn't about making serious progress. It's not even about the whole RPG start-off-weak-and-end-up-a-god grind. You can play it that way, but you'd be missing the point.

It's a stop and smell the roses type of game. It's GTA without the campaign hooks. You know how you fire up a GTA game and just drive around and shoot up shit and do stunts and listen to music sometimes? That's this whole game.

Nothing more, nothing less.