Exactly, I totally agree with you. This is the important thing to remember. Eyewitnesses are notoriously unreliable. And it has nothing to do with them not being trustworthy, intelligent enough, having poor eyesight, or anything like that. It's simply the way the human mind works.
In the late 19th century, people who saw a light in the sky often reported mysterious zeppelins. Seeing the same light in the early 20th century, they reported "ghost airplanes." In the 1940s, it was "ghost rockets," and in the 1950s, the same small dot of light was interpreted as a spaceship. All of these witnesses were telling the truth to the best of their knowledge, and all of them were probably wrong as well. It's not a contradiction.
And it's definitely not just hardcore skeptics who treat anecdotal cases this way. The Swedish UFO organization UFO Sverige has decided not to investigate cases with only one witness and no corroborating evidence. Not because people lie, but because people make mistakes. Investigating such cases is almost always a dead end. You may find that an airplane passed through the exact location at the exact time, but if the witness insists that "it wasn't a plane, it was a huge shiny disc," then there's really nothing more you can do.
And it's definitely not just hardcore skeptics who threat anecdotal cases like this. The Swedish UFO organization UFO Sverige have decided not to investigate cases with just one witness and no corroborating evidence. Not because people lie, but because people make mistakes. And investigating such cases is almost always a dead end. You can find an airplane that passed at the exact time and location, but if the witness persists that "it wasn't a plane, it was a huge shiny disc", then there's really nothing more to do with it.