In a 'Private Little War' there were 3 sorts of people - the Hill People, the Villagers and Nona's people.. In the Cloud Minders there were the Haves and the Have Nots. Also in Spock's Brain there was a great difference between the 'cultures' of the women and the men. In 'The Omega Glory' there were the Comms and the Yangs. In 'Bread and Circuses' there were the Christians and Romans. Even in 'Let That Be Your Last Battlefield' there was that obvious difference between Lokai and Bele.
In ENT in 'The Cogenitor' there were the elite and the sort of slave race.
In most of these cases , it was an "us vs. them" situation...not a spectrum of difference.
The reality is that we need to have several episodes to get a sense of a culture..where we can see people from the same "side" yet be different in personality, how they approach things.
I think too often it was made simplistic by the storyline.