Life on a planet is a lot like a continuous fire, fires often send out embers that start new fires elsewhere.
You send out little packets of life to new places, wait single-digit billions of years (a blink of an eye for the universe, really), boom: new intelligent species with potential to shoot more seeds out into the universe.
What we're capable of != what we're doing / not doing because of political will. We are technically capable of reaching significant fractions of c with tech from the 1960s. We'll never do that because there's no will to do it, but the tech is there.
Same for self replicating stuff. We could build self-contained factories that build stuff from raw minerals, but we'll likely not do it until there's a will for it. Or need for it.
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.
Software, sure. I know 3D printer folks will sometimes 3D print parts for new machines. But nothing that fully replicates itself, right? Especially autonomously.
Maybe we'll see what a moon base can bring us.