The impulse to quantify like this is always fascinating to me in positions like this, as if the only thing a person can muster for a rebuttal is an appeal to some kind of vulgar, assumed utilitarianism. Where are the true believers anymore? Can the ultimately existential nature of humanity really only be of the form "worse-than/better-than"?
People treat the whole world as if they are choosing the right laptop!
OK, here's a non-utilitarian answer: People really like owning and controlling their own stuff. (I suppose you could make that a utilitarian statement, by saying that "really like" means "valuing", but I think it's much deeper than that. It's pretty deep in human nature, from what we observe in almost all societies. So one could say that communism is literally contrary to human nature. You might be able to make it work, but you need different humans than the ones you have.)
This is what I always go back to, if it's so good for people, just do it voluntarily. Organizational problems only get worse at scale. And if people can't be convinced to take part in doing it voluntarily, rather than forcing others to take part, then how is it even going to work out anyway?
People treat the whole world as if they are choosing the right laptop!