It's entertaining, but often comes across as rather idiotic.
Sometimes it comes to a conclusion that makes perfect sense, but only after leading the viewer through a dozen wild theories, leaving you with a sense they were just messing with you.
Sometimes the theories are rampant, but they decide to leave the question unanswered in the end.
Sometimes it leaves the question completely unanswered even though, if they looked for a bit, they could have answers. To Wit: the walls in California in Episode 1. They were baffled as to what those walls are. We have walls exactly like that in the woods all over New England. They're boundary markers, nothing more. Not defense, not ritualistic.. Just walls.
I also find the "experts" they show to be less than convincing, The same person showing up in multiple segments, even when their supposed specialty isn't remotely relevant to the topic. Why exactly do we need to hear from a climatologist about a military base? Did the weather or climate in the area make the base get built faster?
They clearly only have a few actors on payroll to represent the "scientists" they need to pretend this is a convincing show, as they keep using them over and over and over.