I wonder why we assume that most intelligent species would wish to deploy technologies to colonize the galaxy? Especially considering the problems we've had with run-away technologies polluting, degrading, and even killing-off life here, wouldn't a more reasonable assumption be that intelligent species would rather manage their tech (if they even have need for it at all) to maintain and cultivate their habitat instead of having to find new habitats because they trashed their original ones?
Well we shouldn't assume. The two dominant hypotheses for the developmental trajectory of intelligence include "expansion" and "transcension". I'm actually reading about transcension right now. I find it quite plausible and worth further investigation. From the John Smart article I'm reading: By contrast, the transcension hypothesis, also known as the developmental singularity hypothesis proposes that a universal process of evolutionary development guides all sufficiently advanced civilizations increasingly into inner space, the domain of very small scales of space, time, energy, and matter (STEM), and eventually, to a black-hole-like destination, censored from our observation.The expansion hypothesis predicts that some fraction of advanced civilizations in our galaxy and universe must become beacon builders and spacefarers, spreading their knowledge and culture far and wide. Expansion is the standard expectation of those engaged in SETI and METI today. Expansion scenarios typically assume ETI messaging to be bounded by the speed of light, and space travel to occur at some significant fraction of the speed of light.
Living on a single planet or solar system is suicide in the long term. Asteroid, Gamma-burst, anything can kill your habitat. There is no technology than can protect against a gamma ray. I suppose. I read the pdf diagonally cause it's written with obfuscation and unhelpful specialist jargon. So I dont remember if it address the problem , but one popular solution to FP is exactly what you said:
Intelligent species do not need to colonize its galaxy. The problem of most of FP solution (and also this one) is that (as the pdf say) you cannot test them. If you cant test them it become a matter of faith, so not really helpful.