Any person with 1 ounce of common sense would know that it is impossible for aliens to visit earth. with our level of knowledge and technology. But by a people in advance of us by 1000s, 10s of 1000s, millions of years?
And only a person with absolutely zero imagination would declare that, what is possible at the present time for humans, is the limitation for all other beings in the universe, no matter how advanced they might be compared to us humans.
And not just lacking in imagination, but also incredibly arrogant and anthropic.
It is simple math. The nearest planetary system to us inilywsy galaxy is many light years away. It will require 200+ human lifespans to travel there at maximum speed our spacecraft can travel. That is the closest planets to earth
Others are much further away. Can you imagine producing 200 generations in a cramped space ship?
Our universe is extremely sparse. Uneducated is space science do not realize how far nearest the next Sun is to us.