Capitalism

There are exactly two ways for men to deal with other men. The first is by force, and the second is by reason, which in practice means by voluntary trade. For examples of the former, look at the anarchism of the period after the fall of Rome but before Feudalism ruled Europe, Christian rule after that point, fascist rule, communist rule, Muslim rule, tribal rule, etc.

The second is known as capitalism. It is the only social system based on a rational, usable moral code, namely that a man has a right to live. Moreover, his life is not a means to any other or others' ends; it is an end for its own sake.

Observe the social systems proposed by altruists. They first put on the table something which, if it's not "guaranteed" by a proposed social system, they reject it out of hand.

How will it provide for the needy?

They don't ask if man must produce before he consumes. They do not ask if production has any prerequisites. They ask if needy people will be given what's produced first.

Capitalism does ask such questions.