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

[Lauront]

The "new life" might be ambiguous. What isn't ambiguous was that is was significant enough that the populace was divided on whether they could sacrifice it or not. So while they had the means to retrieve the souls, there was weight on the other side about just what it was costing. Otherwise, why would the populace be split? Why would members argue that the star should be left in the hands of this new life if it was not significant enough to mean just as much as the Ancients did?

It's not merely down to what those entities were. A possible consideration would be how those ancients inside Zodiark might have felt about being plucked out of him, which some might've viewed as dishonouring their sacrifice. You will recall that in the original source on the matter, Ere our Curtain Falls, it mentions that the dissidents formed what is described as "no small number". We know Elidibus returns at this point to mediate the dispute. By the time we see Anamnesis Anyder's scene, that support has reduced to just a few. So if I had to speculate? Elidibus conveyed the agony of those ancients caught inside the primal and unable to make a return to the star and swayed the decision on the matter. Because sapient life exists on a spectrum in the setting, and because even the killing of creations was a painful decision for some ancients, it is not possible to simply conclude they were ancients. There are also further practical questions that'd arise, such as how would we achieve this etc.? Too many unknowns, which Elidibus may have helped reduce in number through his firsthand experience of having been the primal's heart.

Once more: I am not saying the route of the sacrifices was the right option, because we lack too many specifics on it, including how they might've reframed this decision if Venat had been upfront about all the information she had. What I am pushing back against are some very frequent assumptions I've seen made on the topic, which don't really follow from the textual material available.