Communism is a stateless, classless and moneyless society. These "socialist states" were always capitalist, in fact, "state capitalist" would be more accurate. Unfortunately, the term "state capitalism" has been used to mean a lot of different things by a lot of different people, so even that is a poor term since it always has to be defined when it's used.
State capitalism in this context simply means that the private nature of capitalism is replaced with the state through nationalization. The private boss is replaced with a state bureaucrat. Wage labor wasn't abolished; the workers are still forced to find employment to gain a living. The difference was that they were employed by the state, not some private capitalist. Everything else stays the same. The mode of production doesn't change a bit, it's only taken over by the state. Private property is replaced with state property, which doesn't change anything for the common worker. For the people, it's the same shit as before, only the bosses have changed. The workers are still wage slaves.
True communism, where the workers actually control the means of production, hasn't been tried, as the state constantly gets in the way.