Marx criticizes capitalism by showing that the idea of value in a capitalist society is based on alienated labor, which goes against the true realization of freedom. This challenges Hegel's belief that substance represents freedom. Marx argues that the capitalist concept of value is flawed and leads to alienation. By rethinking these ideas, we can see that there is a different, non-alienated way to understand value that aligns with true freedom and can work within a free market system.