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.
We also have zero knowledge of, or evidence for, the lack of aliens. The law of parsimony suggests that since we have no specific reason to believe that we're unique in the universe, we should assume that we're not.
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.
This is only true if you believe that intelligent life is extremely rare and/or short-lived.
Also, Fermi’s Paradox.
Fermi's Paradox ignores the fact that human recorded history, and especially human technological history, is a vanishingly short interval of time. Given the abundance in the universe, there's no reason for an interstellar traveling species to be particularly interested in our planet. It seems likely that the only thing remotely interesting about Earth is us, and we've only been a detectable feature for a little under a hundred years (when we started pumping out radio waves). Given the light-speed propagation delay of that information, even assuming intelligent, spacefaring species are relatively abundant, how many can even know we exist yet? For that matter, we may *still* not be advanced enough to be interesting to interstellar travelers. Also, even if Earth is interesting enough for a visit, who's to say they didn't drop by several thousand years ago. How would we know unless they stayed? For that matter, they could have stopped by just a few hundred years ago, and as long as they were circumspect we'd never have noticed.
No, I think the only thing that the Fermi Paradox line of thought tells us is that faster than light travel probably is as impossible as we currently think it is. If FLT were feasible, then it's much more likely that someone within the ~200 light-year sphere within reach of our radio waves might have noticed us and have had time to come visit. Assuming we're interesting enough to visit, that is, which is a big assumption.