A long read introduction to the topic - from We Want to Believe: How Aliens Went Mainstream and Why It Matters
“The search for exoplanets is radically expanding our understanding of the cosmos. “We have learned that the universe is teeming with a fascinating variety of planets, more types than we could have imagined,” writes the astrobiologist Lisa Kaltenegger. But so far, it has found exactly as many extraterrestrials as radio astronomy has: zero. The more we learn about the universe, the more acute the Fermi paradox becomes.”
It is not a paradox, we are speed running towards human extinction. Thus providing a very simple reason why intelligent life doesn’t last long and defines a simple great filter.
What we consider intelligent is quite subjective
Under different definitions, “a forest” could be an inteligent individual
I knew one. He was not at all intelligent.
We are almost certainly an outlier.