All socialist states have been functionally authoritarian oligarchies in practice. I'm unaware of an exception. Someone once claimed Yugoslavia was, but I'm not familiar enough with it to have an opinion.

It's also confusing because there's the notion of State Capitalism (https://en.wikipedia.org/wiki/State_capitalism#Maoists_and_a...) that I believe Marx also wrote about but I don't remember the details off hand. I think this may more or less be the same idea as authoritarian capitalism, but it's also what socialist regimes eventually look like when they realize they need to re-introduce markets to prevent economic collapse.

My take is that the idea of socialism, communism, and capitalism are deeply muddled in theory and even more muddled in practice. Muddled or not, we have people who consider themselves socialists and followers of Marx, their theory is incoherent, and in practice they try to spread violence and destroy any country they take over. We don't really have people clinging to capitalism in the same way, although some right wing factions in the US tried in the 70s during the cold war to make a capitalistic sort of political religion modeled after the success of socialism.

We'd be better off not having to deal with any of these concepts except for the fact that some people have a strong allegiance to these concepts and there's no changing that in the short term. To me it's a bit like when people killed each other over ideas like how to interpret the tripartite Christian God. Is the son a separate person or the same person, and how does the holy spirit fit in? You get an entire tree of ideas, most of which eventually became heresies punishable by death. None of them made any sense but that didn't stop it from being a motive historical force.