You are confusing communism with lower forms of communitarianism, like the transactions within a family of blood relatives and mates, or within an ethnic tribe. A system that scales decreasingly well, the less sexually or genetically-related the participants are. Communitarianism doesn't sever producers from capital, it just changes the incentive structure for production.
Communism is not a system run on selfish genes advancing their own promotion. It's a bunch of randoms taking other people's stuff.