It's the near-humans.Science fiction isn't immune to this, a lot of analysis has been spent on how humans, near humans, and aliens are handled in sci-fi like Star Trek or Star Wars. Especially on how sci-fi reflects concepts of culture, biology and essentialism. More to the point, there isn't a Sci-fi RPG as big as D&D for which to catch that sort of flack with.
Humans with true aliens rarely have this issue. The LGMs can calculate things as fast as computers and faster with them. The Green ones are good at Sociology and Biologiy. The Gray ones are good at Physics. They are all 3 foot fall with big heads and weak little arms.
Even modified humans don't fall into this problem as much as the they are clearly modified and he modification are usually explained.
But with near humans and aliens who become more and more human...