What do you mean by successful? By most metrics, implementations have led to higher life expectancies, literacy rates, and more, when compared to preceding systems. In forms like Worker co-operatives, these systems are more stable than Capitalist businesses with higher satisfaction, and in cases like the EZLN where its more Libertarian Socialist, they have successfully created a community for themselves.
That’s why I tried to ask why you think Socialist states can’t develop, because quality of life follows development, not Capitalism.