I'm aware that you do not identify as a tankie, but I would also guess I'm correct in saying you do not support existing socialist states, which you label as "authoritarian." However, you did provide a handy list of what you think constitutes "authoritarianism," so I'll respond.
Suppression free speech, religion, association, assembly, and the cultural practices of minorities
Religion and cultural practices of minorities are protected in socialist states, so I will ignore them for now as irrelevant. The more important bit is the liberal conception of free speech and assembly, vs. the Marxist understanding. "Free speech" does not exist. Speech is always dominated by the ruling class of society, in capitalism private media is the dominant force and squeezes out everything in opposition. In socialism, capitalist speech is censored. The same applies to association and assembly.
Concentration of ultimate authority into one person at the top
This does not exist in socialist societies, so again, I have to disregard this as irrelevant. See professor Roland Boer's Socialism in Power: on the History and Theory of Socialist Governance for scholarly work on the subject.
Silencing those voicing critical opinions of the state
This is just a return to the Marxist conception of freedom of speech. Criticism is fundamental to how socialist governments advance, capitalist criticism is silenced.
This is why, fundamentally, class must be the basis of our analysis. You erase it from yours, I make it central to mine.