A basic rule of human
Must all Trek aliens be psychologically identical to humans, too? Bad enough they're barely distinguishable from humans; now they must possess the exact same legal structures, too
I'm sorry, but the concept of citizenship is pretty much an inevitability of any civilization that comes into contact with other civilizations. Any such civilization will need some legal basis to separate "ours" from "theirs" -- especially when individual members of biological species start the inevitable process of crossing borders to live within the territory of one rather than the other. Worf is a prime example; if he's going to help make policy for the Federation, then he needs to be
a Federate. He needs to be part of the club, and he needs to hold a status which makes that official. Hence, citizenship.
Concepts like citizenship evolved in real life because of necessity, not because of a cultural idiosyncrasy. Criticizing the application of the idea of citizenship to the interstellar stage of ST is like criticizing evolution as being insufficiently creative because so many creatures evolved bilateral symmetry or eyeballs. It's a function of evolutionary necessity, pure and simple.