I feel like you are both arguing different things. The simple fact of ownership isn't the concentration of power, it's the fact that we don't put limits on that ownership that causes concentration of power. People always argue for or against systems by taking those systems to their absolutes instead of arguing how they should be in practice. If we put a high tax on anyone with a high net worth, high yearly earnings, high estate value, etc., and also take anti-trust laws seriously, then we can largely solve much of that and still operate under capitalism. The problem is more how we are currently operating under capitalism more than capitalism itself, imo.