The character conceptual design space even just around race though is complex enough to dispute you. Even simple examples work, imo:
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Alien races have innately non-human mindsets and impulses, that’s interesting. Its even more interesting when you find some element to it that’s relatable and the cognitive dissonance that creates in the villain and the player characters.
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They frequently have cultures that are insular, reinforce worship of the being giving them negative impulses, and function to exclude them from society even if they do try to repent and that’s interesting.(And only really remains so at the scale to be interesting if its monolithic. Its easy to say “oh that cult’s crazy”, its a lot more striking even if just by scale to say “and that cult is most of their nations and species”.)
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Usually have unique aspects to their race that prompts questions or concern, and that’s interesting. (Derro eyes alone can grab a table’s attention.)