Communism scales horribly and practically begs for intolerant authoritarians to take over because the structure promotes compromise and compromising with intolerance ends up with intolerance. It works well when a small group voluntarily creates a small commune and everyone is on the same page. Everyone being able to see the overall community is pretty important for them to see how they fit in.

Capitalism also scales terribly, but when approached as a competition that requires regulation at least it can scale better because everyone can be watchful of bad actors. It still scales poorly because large companies can gain undo influence over government, but at least that influence tends to be about business and profit and not ethnic cleansing of the ‘wrong people’ that tends to be inherent to large scale communism. Yeah, that can also happen for profit with capitalism too, but again the acknowledgement of necessary regulations can mitigate that for the most part.

Everything tends to fall apart at a large enough scale though.