The argument against this is basically, there are a gazillion other planets. Even with 1/gazillion probability of life on a planet, there ought to be others out there with many being more advanced than us.
However, there are counter reasonings that are about as valid as that line of reasoning.
1. If so, where are they? (Yes, the various things: if there is no faster-than-light travel, they aren't able to get here, and we haven't heard them yet. Or they are here, but want to stay secret. Or they are here and talked to our leaders, but not to us plebeians.)
2. There are arguments that the probability of life (P) is so drastically small that even gazillion x P is small. So we might be it.
3. It took about 5B years on Earth for humans to show up. The universe is estimated to be 14B years old. Thus, in the one example we know, it took an appreciable fraction of the age of the universe for human-level intelligence to show up. What if we are on the quick side. And there will be other human-level (or higher) intelligences, but they aren't there yet.
How possible is it that there are elements out there we have never seen or observed before that could change everything we understand about energy and flight? I certainly believe there are younger galaxies with less population build up, but on the contrary, some civilizations could be just 1 billion years older than us which would amount to a crazy difference in tech. Barring they didnt have their own civilizational issues holding their society down in the dirt. Imagine where we will be in just 100 million years relative to a billion.
Also, its amazing to me that dinosaurs existed like 360m-100M supposedly before humans. The time it would take for the earth to naturally create them, and supposedly be less intelligent is very interesting. I wonder if other earth's develop dinosaurs first? And why did they never organically come back? Differences in oxygen/co2 levels then? Life seems so much smaller than it use to be. Just questions to ponder.
I think much of our history has been manipulated to keep us in the dark but explain things in a narrative that "makes sense" so as to keep us from expanding our minds and the true understanding of where we came from. Both the religious and the elite masons of the world have a win-win because we are essentially lost in the dark and explaining anything outside of the "accepted narrative" is instantly looked as crazy and heretic.
I was telling my mother the other day when she came to the realization that I did a few months ago. She said "back in our day, it wasnt so easy to gather this much information on a topic so quickly". And that's exactly why I dont blame "boomers" for the world's problems. They weren't able to put together connections like we can now and were bascially only fed information by approved sources in Mainstrram media, newspapers, and books. But connecting those dots were so much harder. You didnt have all of these "how to" videos on YouTube or traveling journalist instantly able to get their message out.
This is why freedom of speech is so important, because if we cannot challenge approved narratives with new research and dot connections, than we will not continue to evolve into a smarter society.