Why_do: Your first paragraph is a bit ridicolous, because we can infact see a lot of stars from earth, and those whose we don't see - because they are covered by nebula or whatsoever - we can see weith mirowave telescopes, or radiotelescopes, or x-ray telescopes. So theres plenty of things we can see. We even know where the center of our galaxy(not universe) is. So far, you are right about the planets, we can only assume where they might be by watching for a long long period of time.

But your second statement there is quite intresting. If water would actually really be a not so rare, but actually common - as there are hints of water on mars - and we would find some other traces on other planets/moons, then there would be a way higher chance of human or similar-to-human life existing in the universe.

Still, I belive that life does not exclusively has to evolve like here on earth.