I have a theory about the origin of UFOs: Given the Drake equation, and improbability of aliens deciding to travel thousands - millions of years to specificall

I have a theory about the origin of UFOs: Given the Drake equation, and improbability of aliens deciding to travel thousands - millions of years to specifically this lone planet at less than the speed of light, and then making the mistake of being totally detectable despite having better technology by hundreds or thousands of years, I suspect that UFOs are in fact terrestrial. I had read about the Silurian hypothesis recently, which states that it's extremely hard to detect evidence of a past civilization: https://en.wikipedia.org/wiki/Silurian_hypothesis https://en.wikipedia.org/wiki/Silurian_hypothesis Can it be that these metallic spheres are remnants, either AI or non-carbon-based lifeforms from a past civilization? It's all speculation at this point, but I'm starting to find this theory more plausible.