Saying the problem is selfishnes still presupposes individualism: the problem is that there are individuals who act selfishly and they should stop doing so. It centers the solution around the actions of individuals.

But as socialists, we know this is not the real answer. It is material conditions that force people into competition against one another and isolates us from each other. Socialism will by definition have to be far less individualistic, but you'll still have selfish people.