Applying fancy methodology to numbers you make up helps you think about the numbers you make up. You go from "I don't believe UFOs are aliens" to a more refined opinion of "I don't believe UFOs are aliens because I don't believe X, Y, Z is very likely".
On the other hand, priors are only a matter of the subject. If there are aliens operating UFOs they want or not want to contact us. If they want to, what are they waiting for? If they don't want to, how come our technology can routinely spot their spacefaring machines? Are they that clumsy?
Aliens trolling us could be a viable intention. Billion year old von-neumann probes probably get bored. Or perhaps alien societies are ideologically split and one sect wants to provoke a good or bad response from us per some agenda. Or we’re being subject to CentauriU’s Delta Tau Chi pledge week prank.
And so far they’ve just been lucky and some complex conspiracy requiring they have a fuzzy polaroid filter on all our systems is not required.