Likelihood of aliens elsewhere in the universe with about 2T galaxies we can see? High.
But they are most likely in other galaxies, as the chances of another civilisation in the same galaxy at the same time is remote.
The Earth is about 4.3B years old.
We only have evidence of life going back to 3.7B years ago.
Then, it was just slime, and no multicellular lifeforms until about 1.6 to 1.7B years ago.
Humans have been around for about 300,000years, and only been able to transmit to space for about 100 years.
The Earth is relatively old, and in a "safe" area of our galaxy. So there are many stars where you would not expect to find intelligent life owing to the likelihood of mass extinctions. Added to that, the fact that many planets in the galaxy are not as old as ours, it is highly unlikely that we will be visited by aliens anytime soon. The odds that one will turn up while human civilisation is around is remote in the extreme.
It is likely that there is a great deal of slime in the galaxy.