Even with those simple extrapolations, it’s easy to see that we can stick a few billion ‘humans’ (brains-on-chip) in a solar powered spaceship and just let it hang there for eternity or it could do a journey to somewhere. But what’s the point of a journey as inside this relatively tiny ship, these brains will live in a world (probably a clone of older earth) with a universe around it they can explore.
This seems all rather feasible given time and we would not seem very advanced from the outside; you would hardly be able to detect us at all and yet 100s of billions people live in perpetual paradise (or hell, but again; why would you make it bad if you don’t have to).
Related question is do species really need intellect at all and how much. It could be that the main purpose of intellect is to increase chances to survive, but what if civilisation already figured survival, will they even need to stay intelligent? Maybe their goal is to be happier or maybe have billion orgasms per second.
Another more obvious reason to explore the universe is lack of resources, at least Earth was mostly explored to be exploited. If resources are solved, one reason to explore less.
Most of the financial impetus for exploration comes from the promise of access to scare resources. But if you have the technology to traverse the stars then your species is either able to harness unfathomable amounts of energy such that you can bend space-time or you've done some kind of wild genetic engineering/cybernetic enhancements to the point where it's not really bound by the limitations of whatever biology its planetary evolution set it up with.
In both cases, they would have the means to functionally be living in a post-scarcity society. Either their consciousness is stored in some kind of long-term solid-state storage that can survive millennia long trips through space or energy is so cheap and available that it's hard to imagine them needing to keep going and searching to find more stuff. After you've explored and catalogued a hundred planets it's hard to imagine any real impetus to keep going.
Human civilization is already projected to cap out in population at around 11 Billion, and that's driven primarily by cultural and economic factors deriving from technology around access to healthcare, education, and other sources of diversion/entertainment/fulfillment. The idea that an advanced civilization must necessarily keep growing and growing in size doesn't seem to hold up for our own experience on Earth.
The Caleban have their own reasons for contacting organic sentient species. But be really careful about getting involved in any contracts with them.
We do that?
I have read the sci-fi short novel when I was a kid, and that was 80ies. The future earth have found signs of life on some distant planet and the science ship was sent to investigate, they got there but could not find anything on the empty rocky planet, the somewhat detective story leads them to realize the life is on the star of that system, not on the planet, and intelligent creatures are plasma based life forms. Unfortunately I barely remember this story, and cannot remember the name or author, I've read hundreds of sci-fi back then.
I also read some random popular science post about subatomic processes in cells, it gave some examples of which I recall one that fascinated me, it appears that there is a gate in a cell that opens or closes by a single electron to let a water molecule in or out I guess. This ignited my fantasy, what if there are more subatomic stuff going on in out bodies? How far it can go in reality and in fiction? What if our memory is subatomic? Could we build something on subatomic level, a logic gate for example? Can a life form be fully subatomic?
Also there is a galaxy on the Orion's belt, and the Orion is a cat, they briefly and somewhat humorously explored the idea in Men in Black which I watched many times.
There is quantum realm in the Ant-Man series. If it existed I guess super civilisation would try to go there or stay there to be more energy efficient.
There is also dr Manhattan, whose blue body I believe is photons. Imagine he was not the only one in that experiment, and our entire human race followed him, what would our civilisation be? No buildings, no machines, no crops, no transportation, would we even stay on the planet? What we would do freed from servicing our fragile bodies most of our time? I guess we would just gather together, have fun, party, make new life, teach each other endlessly. So maybe that's what stars are, each just have trillion of dr Manhattan offsprings and that's why we cannot see any signs of life cause we're looking for meatballs.