You are looking in the wrong direction.
Not upward and out, but in...at your DNA if you want to see intelligence prior to Man.
“In this scenario, powerful aliens sit hiding in wait to destroy any visible intelligence that appears. Hanson doesn’t believe that would work because if there were multiple berserker species, there would be opposing parties.”
The Berserkers destroyed all life wherever they found it but concentrated on intelligent life when it was present, unless it could help destroy other life. And it could be many berserker species mutually united in the eradication of life, especially intelligent life. Seems just as valid as his reason for dismissal of the berserker theory.
Maybe the motive to explore or contact others is very, very rare among sapient life. Hard for us to imagine, but we only have an example of one and it’s us. Maybe the galaxy is mostly comprised of super ancient cultures that are just content with their very comfortable homes.
Freegards