The problem with absolutely pure capitalism is that it in practice always puts the rich over the poor. They won't let the government make a policy that hurts them. FDA for instance is against pure capitalism. So are minimum wage laws, child labor laws, basic health and safety laws etc. Under pure cpitalism such laws could never possibly exist.

On the other hand under communist systems, what you think is yours isn't up to and including your own body and mind. You can't protest an unfair policy without jail time. You just found the cure for cancer. Great! now it belongs to the People's Republic of Bendover, and the glorious state will distrubute the cure to the masses. Of course you won't get any reward for it. And you still will work in the same dirty old hospital as before.

Pure systems never work because people tend to try to get power for themselves and not worry about other people. So if you have a beautiful theory, it will never work. Societies just don't work that way. So the best solution seems to be in the middle somewhere.