The Fermi Paradox addresses the famous question: are we alone? Statistically, it’s extremely unlikely that Earth hosts the only life in the universe. Most of the universe is (by current knowledge) unreachable to humans. But let’s look at our own galaxy. Many estimates say there should be at least a hundred thousand civilizations in the Milky Way. If we move forward with the assumption that we are not the only life in our own galaxy — I personally don’t consider that a real possibility — that leaves two possibilities. One is that numerous civilizations do in fact exist, but none of them have spread across the galaxy yet. Each civilization is confined to their local planet, or even solar system. Another explanation is that a galactic civilization does exist, but they have not revealed themselves to us, whether it be because they aren’t aware of us or because they’ve decided not to.
Obviously, I don’t have the answer. But I do think it’s likely that one or the other is true. The diameter of the Milky Way has been estimated to be about 100,000 light years. If we are trying to detect another civilization, we’ll have to observe them somehow. There are two challenges here that could easily explain why we haven’t. First, whatever we observe is really the past. If we are looking at a solar system 50,000 light years away, we are seeing what that system looked like 50,000 years ago. So if a civilization there somehow developed spontaneously tomorrow, we wouldn’t see them for 50,000 years (unless they manage to travel closer to us). The second challenge is that we don’t really know what we’re looking for. We know what life looks like here on Earth. Well, we think we do — in reality, estimates are that we’ve discovered 10% of the species that exist in the ocean. But life elsewhere in the galaxy will almost certainly look different than what it does here; life will evolve under different conditions that those on Earth. All we really know to look for is something that seems out of the ordinary.
I do think a galactic civilization could reasonably exist. But can we reasonably expect them to see us? The industrial revolution is a relatively new thing in the history of life on Earth. Any signs “they” might be looking for, unless they have telescopes powerful enough to see the surface of Earth from a different solar system, will only have appeared within the last hundred or two years. These hypothetical outside observers would have to be incredibly close to our solar system to notice; an observer 300 light years away will see a pre-industrial revolution world. Unless they’ve detected one of our spacecraft (which, again, are within our solar system, so may be undetectable unless we have very close neighbors), they probably don’t know we’re here.
My personal opinion is that until we advance as a civilization to the point of interstellar travel, we will be functionally alone in the galaxy. If and when that happens, I believe we will discover other civilizations and they will discover us, but until then all we have is each other.