The idea that humans should have been able at this point in human history to find evidence of other intelligent life in an incomprehensibly huge universe is the ultimate in human hubris. We've understood that galaxies are galaxies for only about 100 years. We've had radio for less than 150 years. We confirmed extra-solar planets only in the 1990s. We are like children standing on the shore of an enormous ocean who have looked out at the horizon and picked up a few seashells and wonder what else is out there.