It can be built on self-interest, but only if people have conscious egoism.

The lack of conscious egoism is more obvious in the capitalist class. They destroy the world for their own “self-interest”. But that is a contradiction. They, as us, need the world to live. They act anti-socially and destroy the wellbeing of poorer people in their “self-interest”. But we as a species are social animals and only feel as good as the one among us that feels the worst. Homelessness, famine, destitution etc. obviously affect the people directly suffering from them most, but they also affect all of us. We can’t as individuals be truly happy and content as long as people suffer in poverty.

If we were to truly act in self-interest, in a truly conscious way, we would make sure everyone was materially served, had no needs, and could follow their dreams to the fullest. That would be the most satisfying thing for all of us individually.

For the capitalists to enjoy their positions, they have to separate themselves from the rest of humanity. And in many ways, from their own humanity itself.