Ancient Alien theory is the same brand of drivel as intelligent design. A lack of curiosity about the universe leading people to say "a wizard did it".
It also denigrates everything our ancestors accomplished. Human beings aren't clever
, it says. Everything cultured about us comes from outer space. It vastly underestimates what the human race is capable of, and makes massive assumptions.
As a humanist, I see it as no less than a slight against the ancient cultures of the world.