A sci-fi series based on real extra-terrestrials would quite possibly be so alien to us that no one would want to read it.
Not just science fiction and aliens either. Nearly all popular and successful fiction is based around what are effectively modern characters in whatever setting. I remember a paper I read back around the mid-eighties pointing out that Louis L'Amour's characters were basically just modern Americans with the appropriate historical technology and locations.
And happy new year to everyone.