It actually helps the narrative that you can't level up. In most RPGs, you're meant to be this badass one-person army who can, eventually, defeat anything the game throws at you, and in some franchises, literally one-shot God, but here?
You're the only 'survivor' of the fall of the human resistance efforts, with anyone else you meet... enslaved or worse. And it's only due to immense dumb luck, since everyone claims you're not going to amount to much.
By the end of the game, you'll eke out a small victory, but I don't see us managing to topple the mutant leadership. Even when you do make some gains with the attempt to climb higher, you don't defeat anyone.