On Rome. I think basic understanding of inflation would have gone a long way (given their advances, the complete cluelessness of something that seems common sense to us is hard to grasp).
On the show. It reminds me a bit of people who thought there was some lost civilization in the Mississippi River valley because Native Americans couldn't have built the Mounds. While I don't think this show is racist, I do think it undercuts genuine human achievement by wanting to credit an outside force. In that sense, it's a shame. We've done a lot of cool shit over the last couple thousand years. Nothing in our history needs aliens in order to have a satisfactory explanation. That doesn't mean there's never been any contact, but it does make pervasive contact unlikely.