Maybe different races sent different ships for the voyage in the Andromeda galaxy, meaning we'll still Have Some the previous trilogy's civilizations.
My point about characters is That even if MEN is set in the Milky Way, we might still have lost Most fo gen characters we know if some centuries passed After ME3.
No, we'll have colonies. The civilizations are still gone.
Yes, most of the named people we met would be gone, at least in most endings, but the civilizations and possibly descendants of those people will remain. This trip to Andromeda would throw all of that away just for at most a couple hundred random people from each race along for the ride.
That's actually not mentioned in the narrative. They could easily just say "the asari had a contingency ark plan all along", making the asari councilor's words on preservation retroactive foreshadow.
Yes it is. Hackett says he is putting everything into Project Crucible, and after getting the other races to help they do the same because they see it as the only way to stop the Reapers.
They can say that, yes, but it wold be a retcon. And if they're willing to retcon, it makes all the arguments that they won't or don't want to invalid.