This is pretty fair, but there's a vast spectrum of flavors of socialist economies that have never really been executed, or only existed very briefly. Soviet-style bureaucratic central planning is a very limited slice of the possible permutations.

But the fact that the other flavors (say, anarcho-syndicalism) have never existed and seem unlikely to happen anytime soon, DOES speak volumes. Just as it does in the case of purely imagined "pure capitalism".