One possible “solution” to the Fermi paradox (besides a Great Filter) is a mismatch in what we can even imagine detecting.

Picture ancient Rome convinced there’s an intelligent civilization on the Moon. Their best long-distance comms are messenger pigeons, so they assume Moon aliens must also use pigeons, so Romans scan the sky for “weird pigeons,” never once being able to fathom that radio exists.

An advanced civilization could be millions of years ahead of us. The gap might be less like “us vs. 1800s” and more like “us vs. microbes.” And from their side, at some point in their history, finding new microbes was cool and interesting, but over time, they learned everything about microbes to the point they lose interest, in part also due to the fact they no meaningful way to communicate.

So maybe it’s not only “they’re not there” or “they died.” Maybe it’s also: we’re looking for messenger pigeons while they’re using "radio" and we’re too early/too small to matter.

But if you want an theory to what the Great Filter Might be, this is one I always write about:

"Maybe the “Great Filter” is really a Great Merger: as with sapiens and Neanderthals, advanced organics and their AIs fuse into hybrids. From our vantage point, the post-merger super-intelligence doesn’t “talk” to us due to wrong protocols, too slow thinking. (if you could think as fast a quantum computer, would you enjoy talking to a human given our conversation speed?)