re: Some of the best ones are scientists
I know, but most SF authors are not scientists. Nor do they have to be. The science in SF isn't as bad as it used to be overall, but still too many plots of an Evil Alien Force invading the Galaxy and only a ragtag band of misfit humans and aliens can stop it. Or the Star Wars fantasy genre (thanks George Lucas and Harry Potter).
Even in written fiction, too many aliens who are basically humans with funny noses and ears.