But we haven't seen anything yet of the universe....
You are still speaking as the old lady unable to look further then the pond in her garden with only white swans and the woman claiming that black swans cannot exist...
You simply don't know (neither do we) You cannot say that there is no intelligent life on other planets or moons because you do not know.
Imagination is the very beginning of science btw. I do not understand what you have against it. Some childhood trauma or something?
After you imagined something you check if it is true. We imagine that there might be more life in the Universe and now we are working on checking that. At an extremely slow rate now I might add.