Political will is part of the Fermi paradox. So are technical reliability and cultural stability.

The idea that you can just build a thing and send out a swarm and (slow) boom - you've colonised the galaxy, and all the adjacent galaxies - is hopelessly naive. To the point I'd call it stupid and silly.

Let's say you have a replicator thing that works. You send them out in swarms.

And then what? Some die, some miss, some are destroyed by accidents.

Some work.

But "a replicator landed and made some more" is not colonisation. Colonisation implies there's some kind of to-and-fro traffic, maybe trade, some kind of information exchange at a minimum.

And that implies the source civilisation has political, technological, and cultural stability, which can survive an incredibly slow diaspora.

Colonisation worked on Earth because it didn't take long to cross the Atlantic by sailing ship. Successful colonisers landed where humans already existed and trade was easy.

It doesn't work on interstellar, never mind intergalactic time scales, because nothing stays stable for that long. Not hardware, software, politics, or culture.

Nor, on slightly longer periods, biology. On much longer periods, geology, and eventually astrophysics, because stars change, and planetary systems aren't unconditionally stable.

So a colonising wave from a unified culture is an incredibly unlikely thing, not at all an obvious necessity.