I'm not actually a socialist, so I have no passion to argue this, but you could make arguments about how the labor markets are constrained by the current rules

I'm not actually a socialist, so I have no passion to argue this, but you could make arguments about how the labor markets are constrained by the current rules that favor capital (both in legal and tax treatment), so we don't actually know the fair value of an individual's labor in most markets. Also corporate consolidation has suppressed wages and limited avenues for entrepreneurship, so that further reduces the paths to prosperity for most people. Someone would probably also point out that employee wages are hardly guaranteed given that 49 states are at-will, and Montana has fewer people than the city I live in; virtually all Americans can be laid off tomorrow for any reason other than race or other protected status (and even then, we all know there are ways around those laws). Again, I think capital should get profit in exchange for risk taking and organization, but there is no moral argument that shareholders should continue to rake in record profits while working Americans continue to get squeezed tighter every year. At what point does it become rent?