I think cultures can definitely be rated by and advance in the category of how well the people living in it are treated

See, a conversation like this has to be based on a shared set of foundational premises, and those premises can be fairly complex and couched in their own assumptions. My argument is that you can’t describe a culture utilizing the same kind of language that you would, say, a tech tree, where you would need a formal system of writing before you get the printing press, or combustion rockets before the warp drive. That’s not to say that you can’t describe a society or compare its faults and merits, but you can’t really couch that in the language of “advancement.” Advancement is iteration or demonstrative improvement on previous forms, and while the idea of a cultural endpoint is, admittedly, a common feature of materialist philosophical traditions (Marx, for example, believed Capitalism was a stage of economic and social development preceding communism), to argue that it’s inevitable is to argue for something of which we have no real material evidence. Progressive or liberal societies can gradually slip into fascism just as easily as fascist societies can gradually become progressive and tolerant, and there’s nothing that guarantees a clear relationship between societal virtues and technological acumen. Star Trek itself shows a number of very old, very powerful and technologically advanced expansionist empires, like the Romulans or the Dominion, living alongside the more tolerant Federation.