The whole point of the communist paradise is freedom from need.

Perhaps. (I'm not convinced; I can imagine someone saying "In a communist system we will all be slightly poorer because central planning doesn't work as well as markets, but it would be worth it because of the reduction in inequality" or "... because we would all have the lovely warm glow of knowing we were working together" or something. For the avoidance of doubt, I am not agreeing with those claims.)

The lack of incentives (which, I think, exists in Xyrik's scenario [...])

My interpretation of Xyrik's question was more like "Imagine that by some unspecified magic we have solved that problem, so that everyone willingly pitches in to do their bit. What are the drawbacks then?"

I agree that what we're then being asked to postulate is really improbable, and can't think of any plausible non-horrible ways to make it so, but I think the question is a reasonable one to ask anyway. (E.g., perhaps Xyrik is writing some science fiction about a hypothetical race genetically engineered to be much more willing to cooperate with one another than humans typically are, and wants to know what might happen if they tried communism.)

And I agree that if Xyrik were proposing to try this on a large scale in the real world the appropriate response would be somewhere between laughter and terror, depending on our estimation of how far s/he could actually get in making it happen. But that's not the question at issue.