Dude, any theory that is unfalsifiable is, to that extent, a bad theory. You may as well flap your hands in the air and say ‘gawd did it,’ like some credulous revival tent con artist.
Additionally, these “Aliens did it” pseudoscientific “theories” completely dismiss the skill, tenacity, dedication, imagination, and raw inventiveness of human beings. That Ancient Aliens garbage infantilizes humanity, removes our agency, and frankly turns your brain to mush.