Here is the Wikipedia article. But basically it is a response to Fermi’s Paradox that says there are advanced ET’s out there, they just purposely choose not to interact with us for ethical reasons.
My question is, is it mainstream? And could it be true?
I know that I have said before, that some scientists are just too critical, when it comes to ET theories. Roswell and Area 51 are likely nonsense. But Ancient Astronaut Theory has some validity, IMHO at least.