No one is suggesting we're the only life, or even intelligent life, in the universe. There almost must be life elsewhere.
But any society that had FTL does not need anything we have to offer, and even if they did, could either simply take it, or trade for it. They certainly don't need to hide. We can pose no possible threat to them.
Lastly and most obviously, there's no way with all the cameras in the world we haven't seen a photo or video.
My criterion for UFO's is the same as for god. Show me and I'll accept it's real.
What troubles me about UFO believers is so many of them (not all) have this adolescent desire to be 'saved'. Similar to theists, but more extreme, they wish to be plucked out of the misery of human existence into the warm loving bosom of friendly aliens, literally deus ex machina. Gods in flying saucers.