It's easy to look into this subject and see all the ridiculous bullshit and just dismiss the topic. It's harder to dismiss friends and family who reveal detailed accounts of unexplained phenomena. If you look up credible researcher's work (Kahn, Vallee, etc) you'll find that there are a lot of credible people with similar eye witness accounts, in many cases backed by radar.
I'm researched the subject for many years and have arrived at these conclusions:
1) 99% of reported sightings are from stupid people who get excited about a star or a planet or a plane or a bug or a reflection off their camera lens.
2) The remaining 1% of sightings are hard to dismiss, can come from multiple eyewitness sources, can include maneuvers that are incapable of current aircraft, let alone the aircraft of the 60s and 70s, and can include radar and other physical traces.
3) There's so much bull shit out there, doing any sort of research on the topic to form your own opinion is next to impossible.
4) People get really excited about this phenomenon, and either ignorantly embrace it as truth or ignorantly deny it as impossibility. It seems entertaining an agnostic approach to this subject is impossible to most people.
5) The phenomenon covers multiple decades and, contrary to popular belief, nearly every country in the world.
Now I'm not sure what's going on, but it's clear to me reliable people are seeing something that cannot be explained by traditional means. Either people are seeing something physical, or they are seeing something imaginary. If they are seeing something imaginary, that would suggest either that seemingly normal people can suffer sudden (and often shared) audiovisual hallucinations, or there is a group of individuals that possess the technology to constantly hoax people, and have done so for 70+ years. If they are seeing something that actually exists, it suggests that either there are new natural phenomena that produces the apparition of spacecraft, a group of individuals possesses aircraft that defy the laws of physics, and have processes such craft for at least 70+ years, or, that there is actually something flying around up there that is not a product of nature or man.
Any one of the aforementioned causes merits much more attention to the topic than it currently enjoys.