Capitalism is just a continuation of the feudal system. Great for owners / gentry, bad for serfs /workers. Labor creates all value, and should be rewarded as such.
A more morally forceful way to say this is labor is de facto responsible for all production. In other words, labor is responsible for creating the whole product, which has value. By the usual moral norm, legal responsibility should match de facto responsibility. The workers should legally get what they produce