UFO and alien people won’t like this answer, but the aliens would have to have a very long lifetime or at least have had the technology to build a generational ship to travel all the way out here to little Earth.
Given physics is the same everywhere except inside black holes, alien spacecraft would not be able to go faster than a small percentage of the speed of light. Even traveling at the speed of light, however, our own radio waves have not even made a “dent” in the Milky Way. Study the image which I put together for a different question on Quora. An alien traveling for 150 years wouldn’t have even been able to travel a tenth of the distance of the little bubble, so if they’re coming from very far away it would take them thousands or even hundreds of thousands of years to reach here.
They’d have to be pretty determined aliens to travel all that way before discovering if life actually exists here in the first place.