Great subject and thank you for posting this!
However, the issue I have with this is it (somewhat) arrogantly assumes we would know if we’ve been visited. I’m reminded of the flatlander’s story which I first saw on the initial series of Cosmos (miss you Carl; Hang in there wherever you are, babe!).
Perhaps these would-be visitors are like tesseracts: fourth dimensional hypercubes that can’t truly be projected/viewed in our three dimensional world. We may simply not possess the ability to view / sense these kinds of visitors.
While the paradox certainly evokes worthwhile thought, i don’t think it does the “big picture” justice.
Oh, and, good morning GD! (Almost missed the most important part of the post)!