I've always read the "great filter" as some kind of mass extinction. I just think that the Fermi paradox gained popularity when everyone thought that both our travel speeds and our population would continue to grow exponentially, making space colonization both inevitable and necessary.
What if we (and every other intelligent life) just level off when we start reaching the limits of physics and the available resources within our own solar system?
I see it as a galactic cold war. On a galactic time scale, any civilization will reach a technology level of "maximum allowed by physics" relatively quickly, unless physics is indeed an infinite maze of rabbit holes.
Therefore inter-species conflicts are resolved by mass/energy available. Any civilization that doesn't expand to interstellar levels of power is subject to the whims of those that do. If you can expand, you must.
What if we (and every other intelligent life) just level off when we start reaching the limits of physics and the available resources within our own solar system?