If you assume humans are not unique in the universe, you're immediately confronted with the Fermi paradox. If the universe is filled with sapient life, wouldn't some of that sapient life be hundreds of thousands of years ahead of us--a tiny amount of time on the astronomical timescale, but more than enough for them to be observable in some way? Ultimately we're left with the unsatisfying task of speculating without evidence, at least for now.
It could be that life at our current level is more observable to life at our current level than more advanced life would be. The "Dark Forest" hypothesis from 三体 would be one explanation, but even that isn't required. It could be that advanced life can better meet its needs via technology that we can't sense. That was certainly plausible before we could broadcast over the electromagnetic field, which wasn't so long ago. Perhaps it is still plausible, because we're still missing out on something important.
