Ayn Rand's advocacy of self-interest above all other considerations is absolutely right, IF you only care about fairness. If fairness is our only metric, then a pure capitalist system would be close to optimal. There is still the matter of rent-seeking behavior, but that is another discussion.

The problem is, for most people, fairness cannot be the only metric. Some people are just worthless, and they deserve nothing. But we should give to them anyway, because people's fates, and character, are not entirely self-determined. Ayn Rand tries to gloss over this, but it's true, especially for children. Strictly speaking it is unfair and unjust to give to these people. But who cares? I don't want anyone to be homeless even if they deserve it.

On the other hand fairness and justice does matter. It's just as much of a travesty, in my opinion, to make value created count for nothing. The person that provides more value to humanity should be rewarded in proportion to the value created for others. In capitalism, that ideal is realized much closer than in socialism.

So any sane person will choose a mix of the two. And that is what we do. Then we squabble over the exact mix.