What's the point with that quite lackluster story in Endwalker?

[Lauront]

Would they? I thought the reason why Etheirys was so special was because it was ripe with Aether, unless I am remembering incorrectly. Making the journey to other worlds a moot point since they had all they needed on Etheirys. Besides, whether intentional or not, I think Hermes was really the only one to question beyond their star? Which of course would seem odd given most civilizations expand outward in most cases, but maybe it just wasn't an appealing thought to the content people of Etheirys.

I don't see why not. Firstly, let's recall from the Elpis sidequests that they are very open to new perspectives, and to integrating these into their own practices when they appeal to them. Secondly, I am thinking of the scenario where she lays it out all before them: that there are other stars, that are dead due to a variety of reasons, and one of those at least superficially resembles their own, and its people either have or will meet their end. Furthermore, that she's concerned this could happen to them, too, should they not alter their ways. Aside from the fact that I believe this should be their decision to make, given that their primary interest has ever been to act in their star's best interests, I don't really consider it plausible that they'd see their own demise as conducive to that, when their stance to the star is symbiotic/synergistic.

And as tokinokanatae mentioned, they may well take the view that even if they're not all to blame (Hermes is), they at least have a responsibility to help these worlds recover or revive. As these worlds have their own soul cycles, and as the ancients harbour such an abundance of aether that they can create new entities without draining themselves, I could very readily see them taking their perspective and project to new frontiers. What we see in the flash forward scene after Elpis doesn't fit too well with what we're shown in the sidequests, and we have to remember they're still in pain because their star was dying and so many of their people had died, and she was just spitting out platitudes to them.