immediately identify MUST be some kind of alien construct.
My Son The Astronomer tells me that the consensus in astronomy is that we may very well be the first intelligent, technological civilization in the galaxy.
Forget that there are around 100 billion stars in our galaxy, the Milky Way. Some 70% of them are red dwarfs. Which isn't to say that planets around a red dwarf star can't have life, even intelligent life, but it does suggest that such life would be quite different from what we have here.
In addition, some significant percentage of stars are closer to the center of the galaxy, where radiation is a huge issue and would probably keep life from developing.
There's also good reason to believe that not only does a planet need to be the right size, in the Goldilocks Zone, but a decent sized moon may also be crucial.
My Son The Astronomer does exo-planet research. At this point, we can't quite find Earth-sized planets in the Goldilocks Zone. Eventually, we will, because the technology constantly advances.
Oh, something else about interstellar travel. There's A LOT of radiation out there, not simply when you get outside the atmosphere, but much, much more outside the solar system itself. And the faster you travel, the more quickly you are exposed to all that radiation. It's possible that we could develop materials that would effectively shield astronauts from that radiation. But, maybe not.
Oh, and our current fastest rockets cannot travel a measurable percent of the speed of light (c). So rocket technology is another problem. Yes, we are always advancing, and developing a propulsion system that might allow us to travel at 50% of c would be impressive. But the nearest star would still be eight years away.
The problems go on and on.
I read a lot of science fiction, and I love stories that involve FTL (faster than light) travel. I especially enjoy the two series by Jack McDevitt in which humans have happily occupied much of the galaxy on Earth-like planets. The sad reality is that there are probably not very many such Earth-like planets out there.