I've heard this counterargument against socialism/communism for a long time, and it always sounds like a form of "magical thinking" to me. Asserting the tautology that "humans are naturally greedy" when if you know any actual humans, you know this is not true.
Short-sightedness, selfishness, greed, and laziness are all easily handled by a functioning criminal justice system, and public education system. At least in THIS country, we willfully subverted and destroyed these institutions, over a long period of time. For various reasons, but mostly because the haves wanted it this way. The same happened in the USSR.
A few entitled and already very wealthy people are greedy. Most of the rest of us will ACT greedy when they've been deprived of basic necessities by a crooked and rigged system. But by and large, most people are not inherently greedy.