I’ve been visiting posts across different “left” subreddits and in one of them they claimed the Soviet Union was never socialist since they got stuck in state capitalism and not even under Stalin they were truly socialist (in fact they claimed it was authoritarian and horrible, but I won’t dismiss their main opinion only because of that point).

So, basically they mention that despite the apparent benefits the people had, workers were also exploited as their regular capitalism counterparts since they lacked any real power over their labour.

Are they right? Does the mere fact that workers owned or not the means of production refutes or proves they were socialist?