Another possible explanation against the fermi paradox could be that interstellar communication, let alone travel is much more unlikely to occur even among highly advanced civilizations. maybe just travelling beyond our solar system might remain uneconomical for a long time.
Its conjecture is that physical travel to other civilizations is so expensive, and light-speed communications are so slow and inefficient, that the only way highly advanced civilizations communicate is by digitizing their consciousnesses and transmitting those, to be run in simulations on the receiving end. However, since you wouldn't want to transmit a copy of your own consciousness to an alien only to have it tortured or worse (even in a simulation), there are very extensive negotiations around trust involved before full contact with other civilizations is established.
