But you’re right, I’m forming the opinion that if you’re that advanced you can essentially choose what size you want to be. And if you can do that - and eg live on the surface of a red dwarf for billions of years - why do you need to be expansionist at all? Is it for the view?
Not only do you have to have the technology to do any of these these things (which is not a given), but somehow you have to have a civilization dedicated to doing it over the course of thousands of years.
No. Just no. It’s just fantasy.
Case in point: We know there are no type 3 civilizations anywhere in the observable universe. V
Therefore - why expect advanced civilisation to be detectable? Just because you could be type 3 doesnt necessarily mean you have to be.
Arguably you might _not_ want to - considering 3 body problem game theory and potentially accelerating the heat death of the universe.
Or maybe they all just leave. Or maybe they don't exist.
So to say its fantasy is essentially assuming we've proved a negative. That's not a hugely rational position to take.
That's my take anyways, I'm a programmer not mathematician.
The next step for us as a species is trying to survive on this planet in the long term. Not nearly a given.
Speculating on what far away, far more advanced civilizations might be up to is just for entertainment, nothing to take seriously.