Well, compared to capitalism its much more utopistic - I mean how far it is from reality of human nature and how much you should expect from people in the system.

As history shows us numerous times, it really doesn't matter how good things look on the paper or during academic discussions. The reality is, evil, messed up, unbalanced, sociopathic etc. folks are part of society. I don't mean in insane asylums, I mean in schools, hospitals, corporations, hackernews, everywhere. And somehow, for number of reasons, when numerous factors combine these people rise to power although they shouldn't. Every communism I am aware of ended up as dictatorship very quickly. In real capitalism, they come and go much more quickly and the impact is smoothed out over time.

This is the breaking point for me where the system is obviously worse - in communism, those dictators always ended up as net loss for citizens and mankind. And you gotta be brutal if you want to force millions into situations they wouldn't choose themselves. There are other obvious issues - no private ownership means nobody will work hard to maintain/enhance/create if at the end benefits are marginal at best. Better enjoy that beer.

And over time, these things compound and the result is always the same. Capitalism wins through sheer efficiency and overall upper hand. When comparing similar starting systems, its pretty clear which is more beneficial.

But yeah, it looks cool and very nice on the paper, or in TV like Star Trek.