Sci-fi tends to reduce all planets to monolithic cultures or two at best but it seems more likely each other planet would be as rich as our own with different languages, religions, cuisines etc
@anon_opin It's not that unrealistic though, some planets could be relatively new colonies with 1-2 dominant cultures. Guess depends entirely on what sort of universe setup it is. Like, I can imagine a galactic federation or empire sees planets like individual regions and interplanetary dependency made people identify more with their planet like people do with nations today.