To me the Fermi paradox is easily explained by the speed of light being a hard limit on how fast something can go and the fact that space is absolutely enormous. Every expectation of multi planet civilizations simply hand waves away physics. How would they move between stars? "You know, alien stuff. They'll figure it out."
There are also unstated economic assumptions that don't make a lot of sense. Why would they leave their planet anyway? A civilization wealthy and advanced enough to consider traveling to other planets probably does not have a population big enough to support the kind of large scale emigration needed to set up big colonies. Wealthy societies have fewer children. Then of course there is the question of why would you ever leave a planet with such advanced technology and apparent wealth? I would much rather live in any city on earth than a colony on the moon or Mars. How long would it take for those colonies to be as attractive a living space as the place we have right now?
There are also unstated economic assumptions that don't make a lot of sense. Why would they leave their planet anyway? A civilization wealthy and advanced enough to consider traveling to other planets probably does not have a population big enough to support the kind of large scale emigration needed to set up big colonies. Wealthy societies have fewer children. Then of course there is the question of why would you ever leave a planet with such advanced technology and apparent wealth? I would much rather live in any city on earth than a colony on the moon or Mars. How long would it take for those colonies to be as attractive a living space as the place we have right now?