Also, what is it when everyone owns them (in varying ownership percentages of course) via index ETFs?
Marx was wrong not about if, but about how the workers would take control of the means of production!
That's the beauty of it, since the workers still don't control the means of production. But they do depend on the valuation of their "portfolios", so they're invested in the continued existence of the system, and they're pitted against each other as they are both labor and owners. But not enough owners to matter.