It’s a group of idiosyncratic people so there are not hard guidelines but there’s definitely a hierarchy of who they are more likely to describe as advance civilizations and who they question were capable of major engineering projects. This can bring out really weird stereotypes: I’ve heard people make arguments where they positively describe American Indians as living in harmony with nature, etc. but question the estimated populations, trade networks, etc. for e.g. the Mississippi tribes from what appears to be a mix of “noble savage” mythology and sort of mentally having slotted them into a larger model which made it easier to doubt one detail than reconsider their larger intellectual framework. The “aliens did it” people are far out on that spectrum but less extreme versions aren’t uncommon.

There you go trying use logic on racism. Of course it's not going to work.

The question isn't whether the ancient aliens framework logically supports racism, since it's false anyway and racists don't care about logic (otherwise etc etc). The question for racists is which frameworks most conveniently provide tidbits for them to distort for their own purposes. No logic, pure association and confirmation bias.