I have watched your lecturer on youtube about Socialism. I don't understand why Stalin didn't just made the transition to reorganize enterprises. Instead he substituted the wish for the society and told the them that they have "achieved" socialism. But why didn't he use his power to reorganize the factories, the offices, the stores, ... so they would work in the interest of the community and the whole community would be making the decision. Because then he actually would have achieved socialism, or?
People are mostly prisoners of the ruling ideas of their time. Stalin was too. Socialism then was conceived as government taking over production (state enterprises) and govt planning the distribution of goods and services. Stalin focused on that as did most socialists and communists until the last years of the 20th century. However, the weaknesses, shortcomings and eventual failure of the USSR has provoked socialists everywhere to rethink their most basic ideas including how to define socialism. They increasingly move to a definition that includes or even foregrounds transforming enterprises' structures from hierarchical capitalist to worker cooperative non-capitalist.
This argument is developed in great detail and systematically in S. Resnick and R. Wolff, Class Theory and History: Capitalism and Communism in the USSR, New York and London: Routledge Publishers, 2002.