For the quarter the cost of Twitter you could build a pretty sweet Earth monitoring station on the surface of the Moon. It makes zero sense that aliens with essentially magic space travel technology couldn't do the same and go completely undetected by people on Earth.
The scale and scope of "building a telescope" and "building an interstellar spacecraft" are not just comparable but directly related. I'd also assume such a civilization would have a good handle on diseases, at least have a strong understanding of them.
It turns out that the civilization on Earth that landed on the Moon also had a pretty decent understanding of disease. By the time of the Moon landing many diseases that wracked the world in the 1500s were well under control in the first world. Some were even eliminated.
This is evolutionarily sensible: we're a tribal species with a group-collective survival strategy, but few natural defenses: no fur, poor night vision. We're almost entirely dependent on tool-using to exist in the wild, it's our edge but it makes us very vulnerable.
UFO reports disproportionately occur at night, and also from relatively isolated people. It doesn't matter how smart you are, it's almost impossible to turn off those primitive senses which tell you "you're in danger, you need to be aware". Being afraid of something which is not there and avoiding it is a vastly preferable strategy if it also means you're afraid of something which is there.