"Unlikely" is probabilistic terminology. Indeed, the so-called Fermi Paradox is said to be based on probabilistic argument: Drake equation - https://en.wikipedia.org/wiki/Drake_equation
Lets have a look how the probability in question is calculated. From wiki:
We can see immediately, or we can read it in wiki, that number of parameters are speculative with ranges varying greatly.
Then the question to me is, how useful such estimation of probability is and if its possible to base any sound argument, the so-called Fermi Paradox in particular, on it.