Do you believe that Aliens have already Visited our Planet

I believe in both the idea of the existence of aliens, and that they have most likely already visited our planet, even if only for research or sample collecting rather than for interaction with us as a species.
I do not necessarily however believe they are responsible for the various unexplained statues and monoliths in multiple locations in the world, after all, why would the remain anonymous and yet leave likenesses to themselves all over the planet?
The recent trend of a massive amount of reportings of alien abduction i also believe to be false, as nearly all of these cases can be attributed to a type of sleep disorder, where the victim awakens paralyzed and suffers hallucinations as well as a sense of dread (sleep paralysis), of which aliens, witches and demon visitations are all common delusions.
In an infinite number of planets in the universe, it logically follows that there must be an infinite number of alien inhabited planets as well, some of which are likely much more advanced than mankind and some of which are likely more primitive. this fits with the idea that there have been visitations in the past, and if the aliens are much more advanced than us, (which they would need to be to have traveled the massive distances from the nearest life sustaining planet) they might not want to have interacted with us because we are not ready, or are too unintelligent to be able to communicate with them. It ancient cultures there are also references such as ‘men of the sky’ and notions of demons and angels descending upon mankind from the heavens (heavens being the term for space rather then the idealistic intangible idea of heaven in this case). This fits with the idea that they don’t want to communicate with us yet, as in ancient times they had lass chance of being detected and less chance of hostile reactions.