The ground assumption in all of this is that we have some comprehension of the technological end-game / plateau. I.e. that a civilization far more advanced than our own will still care about solar energy and EMR communications. Who is going to build a Dyson Sphere for fun? We could be totally wrong about this. We probably are.
The other possibility is that there's not much more technology for us. Can we build self-replicating probes that can operate, without maintenance, for thousands of years? No we can't.
So we have this wacky set of assumptions -- that alien civilizations will be more advanced than us in certain peculiar ways (able to build self-replicating probes and/or Dyson spheres) but not in others (having the primitive needs and side-effects that we do). This is a tiny corner of a very large set of possibilities.
Maybe the aliens simply build new Universes to order and leave their birth universe behind because it's (a) less hospitable than their new "air conditioned" universe, and (b) it's unethical or boring or pointless to colonize a universe full of new potential civilizations.
Folks need to read some less mainstream SF. I like Clifford Simak's "City" where the vast majority of the human race emigrates to Jupiter to live as hunter-gatherers (because Jovian life is so much more pleasant than human life) leaving Earth to the dogs, robots, and ants.
To be clear, "self-replicating probe" includes all technologies that can transport, at a minimum, human genetic material, a record of all human science and technology to date, and creche-building technology to a distant star. So a few grams or kilograms of bootstrap molecular nanotechnology, computing material, shielding, some form of reaction engine, fuel for deceleration, and fired by the hundred from a solar-system-wide array of magnetic accelerators or accelerated by lasers. More likely the human genetic material will be absent in favor of emulated human minds.
Or think about actual humans, something large that we'd recognize as a starship, and a vast amount of antimatter. Much more spectacular, and much less likely, because of the amounts of energy involved in getting the job done - and all that just to ship things that could be build on site.
The point being that even if you say that we'll never build self-replicating technology (which is essentially the same as being a vitalist) then given the time scales involved - if every step in the probe network takes 1,000 to 10,000 years of resting time to build a complete organic human civilization before kicking off the next series of probes - it still requires a short time span to visit all stars in the galaxy in comparison to the age of the galaxy.
You're still making ground assumptions that this kind of technology turns out to ever make sense. If we invent transdimensional warpgates in 50 or 500 years, there may never be a faction left over that wants to play with steam-powered genetic plagues.
The idea that you can seed the universe with civilizations in the manner described is highly dubious. You're assuming someone advanced enough to do this yet primitive enough to want to do it and that "it" works at all. Suppose that the galaxy produces one star system in a thousand with a suitable planet, and the seed has a one in a thousand chance of actually producing a successful replication. (Both of these one in a thousands seem to me to be quite optimistic.) The equations look a lot less deterministic.
The other possibility is that there's not much more technology for us. Can we build self-replicating probes that can operate, without maintenance, for thousands of years? No we can't.
So we have this wacky set of assumptions -- that alien civilizations will be more advanced than us in certain peculiar ways (able to build self-replicating probes and/or Dyson spheres) but not in others (having the primitive needs and side-effects that we do). This is a tiny corner of a very large set of possibilities.
Maybe the aliens simply build new Universes to order and leave their birth universe behind because it's (a) less hospitable than their new "air conditioned" universe, and (b) it's unethical or boring or pointless to colonize a universe full of new potential civilizations.
Folks need to read some less mainstream SF. I like Clifford Simak's "City" where the vast majority of the human race emigrates to Jupiter to live as hunter-gatherers (because Jovian life is so much more pleasant than human life) leaving Earth to the dogs, robots, and ants.