And the subset of that group which is willing to accept that aliens may be the most likely answer, based on current knowledge and theories.
Since we have zero knowledge of, or evidence for, aliens, I don’t see how that can ever be the most likely answer. Considering that we have no idea how life arose, and that all evidence indicates that it only arose once in the one place we know it arose, even though there are certainly a lot of stars, we can’t really make useful predictions from a sample of one. When you consider the immense distances between stars, and the vast aeons of time our galaxy has existed, even if life had arisen elsewhere and, against all odds, evolved intelligence, the chances of them being our contemporaries is, well, astronomical. Also, Fermi’s Paradox. If, and when, we begin to find evidence of biological activity elsewhere, then we might be able to say something about it. For now, it’s all pure speculation. Plug any numbers you like into Drake’s Equation.
Intelligent aliens are only slightly more plausible than gods. Which is to say, not very.