According to this study, we haven't really met the aliens (officially speaking) because the universe is too big and it would take them too long to probe it and find us at the time we are developped.
There's probably some truth in this, but it considers that travelling at the speed of light is not possible or even close. But it's already possible in labs. It doesn't take in account teleportation that already exists in labs too, the use of dark energy, maybe telepathy and all that stuff we don't understand yet. So I think the answer is not there yet... Maybe we are the first ones to be that advanced in the universe ? Or that the matter is not travelling, only the souls ?