It's not at all difficult to make an argument that we have not been visited by aliens. e.g.,

https://www.reddit.com/r/changemyview/comments/1468rqs/cmv_e...

https://marginalrevolution.com/marginalrevolution/2022/05/th...

among many others. I think this comment from the marginalrevolution link is compelling:

"I write science fiction professionally, and I would cheerfully bet against these sightings being any alien technology. Why? Because zooming around in Earth's atmosphere and playing chicken with fighter planes doesn't fit any rational notion of why someone would go to the considerable trouble of sending a mission to the Solar System. (Jokes about alien teenagers aside.)

If the goal is to make contact, then there are much better ways of doing it than flitting around the atmosphere being coy.

If the goal is not to make contact, then contemporary human tech could already do a better job of observing while staying hidden. A big telescope on a near-Earth asteroid could watch us in considerable detail during close approaches. Small satellites could do the same. And small robotic probes disguised as -- say -- seagulls or cats could do all the sampling and exploring of the Earth's surface with nobody the wiser.

As it is, we have a phenomenon dating back at least 70 years and possibly thousands of years which never seems to DO anything.

My conclusion: it's probably a lot of different phenomena, mostly involving human perception. Maybe, if we're very lucky, there's some rare atmospheric phenomenon causing some of these sightings, and we might learn a little by studying it."

(It's also easy to make an argument that we have been visited by aliens, in the same way that it's easy to make an argument that the Earth is flat or that humans never landed on the moon ... easy if one doesn't adhere to basic principles of rational discourse.)