This is the human nature fallacy. It’s twice wrong, because it reduces all human nature to a single characteristic; and because even if that statement is true, there’s a logical contradiction in it.

Socialism and communism is not about rejecting greed, or even about upholding any moral value or even about denying or upholding any human characteristic. It’s about workers taking power and re-organizing society so workers are the ones on top. That includes oppressing the capitalist class and eventually getting rid of them.

So even if you are a self interested worker, is it in your self interest to be subjugated by capitalists? A greedy worker should accept submission by another capitalist?

And you can still be a greedy and self interested worker, even under socialism or communism.