The question isn't whether Communist societies can exist; they did for millenia prior to the Neolithic revolution. The question is whether advanced Communist societies can exist. I believe they can and inevitably will occur; just that we won't see them for at least another century. The goal right now is to advance technology to the point where scarcity no longer exists as a meaningful limitation (socialism). Once that is done, the notion of money, labor, private property, and statism will evaporate.
Objectivism is so obviously defective as a political theory that it fails in principle alone. Simply apply the test of universality to it. If everyone looked out for their own self-interest and didn't care about others' welfare, then people who were incapable of looking out for their own welfare due to disability or social conditions would simply die. This is obviously immoral, so the system fails.