Just because a humanitarian intervention is doable in one scenario (because of population size, resources, etc.) doesn't mean that the Federation would somehow be forced to intervene throughout the galaxy.
Well of course not, it would be a question of priorities and assets.
Yes, but I'm talking about setting a precedent for Homeward-level types of crises. The ones that would require thousands of starships working around the clock.
This has already been addressed.
, have the Prime Directive policy include that when a species is facing utter extinction that Starfleet can move all or part of the species off the doomed world. Direct contact with a primative (or not so primative) species.
Because survival trumps contamination.
, this doesn't mean the Starfleet then has to endlessly prowl the galaxy looking for species to move. The only precedent that would be create is that the Prime Directive recognizes that not all situation are the same. If Starfleet has the assets availible, in place, at that time, great. If not then a tragedy will occure that is in no way Starfleet's fault or responsibility.
I could imagine that during the Dominion War a Humanitarian evacuation would have been out of the question.
Which simply isn't practical. Your level of help also depends on how practical that help is. It simply isn't practical to move a planetary population.
This. It unlikely that a entire planetary population in the tens of millions (or more) are going to be moved. Starfleet is simply going to have to employ some kind of selection process. to the majority of the population left behind (abandoned) on the doomed planet the selection process wouldn't be seen as fair. The people moved will have to be people who can re-establish their culture on a new planets, while at the same time being able to feed themselves after a short period of time.
Unless we want them to become dependent on Starfleet's on going assistance.