Instead of bemoaning the weak aspects of capitalism, why not emphasize its pluses?
In a perfect world, everyone would have equal intelligence, equal bodies, and equal ability to produce goods and services. They would also have uniform distribution of resources and equal transportation. If that were to happen, then social justice would be to have everyone earn the same wages and be able to buy the same products at the same price… If they all had equal needs, then distributing wages equally would make sense.
No economic system will be perfect because humans are not perfect, and the earth was not designed specifically for imperfect uniform human habitation. Utopias have been tried and failed numerous times in human history. The only system that will prevail will rely on the natural tendencies of humanity in the face of advantages and disadvantages existing in the means of production and the markets for its products. Theory that goes against human proclivities in the face of uneven availability of resources and markets will never work.