Is this really a function of capitalism or just who humans really are in general? That is to say humans are self interested and desire to maximise their own wealth.
Capitalism is designed to force everyone to maximize personal wealth, because wealth determines resource allocation. Other societies did it or do it differently.
You do not have to 'maximize' your personal wealth and nobody is forced to do so. Many people choose to do so, voluntarily. That's the essence of free markets. It just so happens capitalism not only complements the notion of free markets, but enables more markets to exist than otherwise.
You can't have it both ways.
In capitalism, yes.