>>213651581 (OP)
Well, there are really only a few possibilities given that such ludicrous amounts of time have already transpired.
1: Space travel on an interstellar scale is impractical and nobody does it universe-wide. Otherwise we would through brute force of time and odds have encountered it by now.
2: There are no aliens at all. Intelligent life is a radical anomaly to the scale of being unique.
3: The entire universe has some sort of treaty or common-sense reason to be as subtle and noncommunicative as possible, to the point that NOBODY has gone out of their way to create some big obvious beaconto the galaxy in a highly visible way in all the billions of years of its existence.
It is commonly said (by idiots) that there is "No stealth in space," because the failed writers at Atomic Rocket don't know how resolution works--it's easy to avoid visual detection, but less so to leave no trace whatsoever. It is very conspicuous given that the universe has existed in potentially life-producing form for millions of times the history of life on Earth, and yet we see NO evidence of alien visitation. They didn't leave a satelite to monitor the obviously habitable planet? Why not? We would, and it's not like it'd just be one alien species, if there were aliens and space travel were feasible you'd expect someone to have stumbled over Sol a few times.
One theory is that Earth is just highly remote, we are in an unusually less dense are of space, it might just be that we aren't important enough to visit, but even then, why not send a drone or something? It's been billions of years!