In Cuba it seems to "work" okayish. I've been there myself. Although people are poor (in our view) they don't seem to mind much, they have what they need. Capitalism does increase overall wealth though. But it also needs a lot of regulations and control, otherwise (big) companies optimize for themselves (monopoly abuse) or form a cartel. It's not black/white.
Cuba? Really? You're going to hold Cuba up as a shining example and just completely ignore their human rights abuses?
Oh wait. I forgot. You're in favor of communism. I should have known you wouldn't care about human rights.
The right of the individual to succeed and excel and be rewarded for his or her* work is paramount to my philosophy. When success is penalized by a society, that society is not one I want to be a part of and is one that I will fight against with every fiber of my being.
*(I said "his or her" because there are only two genders. REEEEEEEEEEEE)