...is, what are we looking for?

Or, are we just looking to know more?

All the old interplanetary SF followed tropes from adventure writing from 19th Century explorers and painted the venture to Other Worlds as being more of the same - aliens were usually added to the White Man's Burden, or were equally Imperialists and probable combatants in cosmic wars, or they were Angels & Demons made flesh.

As we developed the technology to carry us to other worlds, we also developed a realization that the Alien wouldn't be "just like us" or like anything we knew at all. I don't think that has been fully assimilated just yet, because in our ignorance anything is still possible. DNA-RNA genetics could be strongly constrained by physics and life could be a deterministic process that inevitably produces humanoids. Or chemistry is largely irrelevant and a deterministic set of "forms" or attractors means that the same biochemical apparatus, regardless of substrate, will be produced. We don't yet know.