These people are self-congratulating, self-appointed experts, whose knowledge of ancient history and science is at best flawed, if not completely fabricated. Of those mentioned, only Sitchin has any real post-secondary education, even though his degree from the University of London was in economics and not archaeology or ancient languages. They do tend to be well travelled, but visiting a place no more makes you an expert on its history and nature than looking up makes you an astronomer.
As I’ve mentioned before, I find it insulting that most of their theories reduce the real history and science of many archaeological sites to a steaming pile of wild speculation and conjecture. They diminish the achievements of our ancestors and demean our long lived legacy. I don’t deny that the idea of extraterrestrials visiting our ancestors is an attractive one, hell, I’m prone to believe that aliens are visiting us now, but if we’re accepting the flawed and often times fraudulent opinions of people who’s own past is peppered with plagiarism and “poetic license”, we’re accepting a lowered standard of evidence that can only lead to embarrassment.