You're right in the sense that authoritarianism isn't exclusive to Socialism, but every time Socialism has been tried it has led to authoritarianism, oppression and tyranny. If you tried to apply it on a global scale, the results would be catastrophic.
The problem is that Socialism is an intellectual concept. It sounds great on paper and when discussed by smart, educated (And typically, middle class) sociology students in university common room bars.
(Back in my days, late 70's, the STEM students were pretty much all Tory, and with a fair few NF thrown in for good measure!)
But in the real world it flies against basic human nature.
To have any hope of working as a practical system, it requires that all members of society are willing to suppress their basic natures and go along with it.
This doesn't happen and as a consequence a high level of authoritarianism (Right up to the mass slaughter of those who are unwilling to "Get with the program") is inevitable in any society that attempts to implement it.
In addition, Socialist utopias are inveitabally really rather contrived.
For your homework, I recommend the most influential book that nobody has ever hear of.
"Looking Backward" by Edward Bellemy. p1888.
It seems to be largly forgotten today, but in the late 19th century. "Looking Backward" achieved a status and influence comparable to "Das Kapital"!