Capitalism has nothing to do with harnessing greed.
If you want to try an engineering analogy think of Economic systems as Control Systems linking allocation of resources and production to what consumers want. Capitalism is the best system because it has feedback in the form of proftis and loses. Entrepreneurs take an educated guess as to what people want and how to arrange resources to meet that demand. Freely set prices let them (and the rest of the market) know if it's a good idea (profits) or bad idea (loses). If you make loses it means you are not using resources efficiently and those resources are freed up. If you make profits it means you are doing a good job and you get more resources to work with. If you make "Outragous" profits this gets the markets attention and other people will move into your market driving down profits towards an economy wide average.
Every regulation and political policy that gets in the way of this process makes things worse. Central planning by definition means overriding consumers choices and makes things worse.