But those who have disproportionate amounts of cash don't consume as disproportionally as they earn. An individual can only personally consume so much. As more wealth is concentrated in fewer and fewer people, the money that trickles down as consumption declines. And as investment becomes more and more abstract, you've got algorithms passing money back and forth between algorithms, and the rate at which cash actually makes it out into the rest of the population also slows.

This is true, but if you take Piketty's argument that historically the return on that capital is greater than overall economic growth, then labor, being primarily reliant on economic growth for increasing their wealth, never catch up to the capitalists.