I believe this is called "Fermi's Paradox."
Enrico Fermi postulated that any civilization with a certain level of proficiency in rocket technology and sufficient ambition should be able to colonize the galaxy within something like twenty million years. Now, twenty million years sounds like a lot, but it's peanuts compared with the age of the galaxy which is measured in thousands of millions of years, and not even all that much on the geologic time scale we use to measure the age of the earth. Twenty million years ago was already the time of the Autralopithicines.
Fermi then asked the obvious question: where is everybody? That there are no aliens openly walking around seems to imply that there aren't any. Or, that if life does occur elsewhere in the universe, it is uncommon enough that it is isolated by vast intergalactic distances and the result is much the same.
Most answers to Fermi's paradox seem to revolve around anthropomorphizing the aliens, that they have some cultural reason to remain secret like a Star-Trek prime directive. The alternative is the anti-anthropomorphizing argument that the aliens are so different that we cannot detect, understand, or comprehend their communication. Neither of these answers are particularly satisfying, in my opinion.
Supposedly, those postulations slip thru
the real realities
like water through a sieve for a list of reasons I couldn't begin to guess at, much less articulate.
If one's impressions from folks who 'know' are to be believed.
I think you have more correctly described what I read.
It just got me to thinking about where they would actually have to originate from, and what those implications are. Absent some time-space travel bend by going the speed of light, they would have to come from our solar system, which does not appear to have even the most remote chance of happening.