Humans are certainly not too stupid. Alien life is definitely extremely rare. And when something is rare, nothing will be considered too stupid. The analogy of a child randomly calling other houses doesn't apply, because children on this planet are not rare, they are common.
Sorry for nitpicking, but it is the stars that are rare (relative to expected travel speeds and costs) that make aliens rare. We don't have no clue how rare aliens are beyond that. They could be as near as Alpha Centauri and as far as ten galaxies away, and we have no way of telling. We've yet to find the means to reject the possibility of advanced alien life even around nearby stars, rejecting them or confirming them at distances further away might be forever impossible.
This is an important distinction, because the rareness is solely due to the travel speeds and costs, and if we underestimated them significantly, then Alpha Centauri is suddenly the house across the street, and life suddenly becomes common even if there is as much as a tribe of space monkeys there.
It would be even so if aliens perceive time in a different way. Or deal with long periods of time in a different manner. Or if they are on to colonizing the galaxy (which is not all that hard, by the way) – if they are everywhere, suddenly even the rare aliens become common for them, because they would have counted millions of us rarities along the way.
So in all certainty, it is not "definitely".
Space travel is pure luxury. You will only travel to other star systems if you don't have any other problems left.
Or if we saw further than the end of our noses and did long-term plans for our survival.