That's like bacteria in a Petri dish saying: "I struggle to believe that The Pipetters are objectively real because I have a basic grasp of the size of the lab

That's like bacteria in a Petri dish saying: "I struggle to believe that The Pipetters are objectively real because I have a basic grasp of the size of the laboratory room, how much of it is just empty, how hard it is to travel between the bits that aren't, how inhospitable almost all of it is to bacterial life, and because everywhere we look it seems primordial and uninhabited. I don't think that is prejudice." Don't forget, we're mind-bogglingly primitive and ignorant. We don't even know the laws of the universe yet! (ie unify GR and quantum mechanics) Of course we haven't figured out UAP-type technology, whether what we're seeing is interstellar travel or something more exotic.