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

[Brinne]

Sorry to see you go, Lunaxia, but of course, I understand.

As far as the sacrifices go, my genuine impression is that the intended "vibe" - once again, the game is, thus far, absolutely unwavering on this point - is that that self-sacrifice of the Amaurotines is meant to be understood as something absolutely noble, breathtakingly heroic, and as Alphinaud's stunned silence reflects, something we understand is a level of "goodness" beyond modern humanity. As far as the precise mechanics, if you want to shoot the breeze about that, I would guess - because this is another thing I don't think the writers actually sat down and mapped out concretely - that while there were probably some mutterings at the time of the sacrifice about maybe, hopefully, finding a way to save the sacrifices someday. It's clear that they were committed sorrowfully, understanding they were being sent to a horrible fate, and Zodiark was designed to keep their souls preserved, after all.

However, everything about this plan was also completely unprecedented, untested, and hypothetical to the Ancients, and they weren't even sure that the aether shield would work at all (since, again, they were completely flying blind about the nature of the Final Days) - so they had no idea of knowing if there actually would be a viable possibility of saving the sacrifices after the fact, and those people knew that at best they had a huge, guilt-ridden uncertainty about those chances when they marched to the gallows. From Shade Hythlodaeus's description, it sounds like once everything had settled down and the planet wasn't actively dying, they finally sat down and got their heads together to figure out how to move forward and what their options might actually be from there.

That would be my best guess on the general flow of things - and I don't think it in any way undermines the nobility of those sacrifices. As I said before, the attempts to do so seem at best, to me, extremely cynical and probably a bit mean-spirited. We're not gonna give the Ancients any credit for goodness, even in a breathtaking gesture of selfless benevolence that every living creature in the world owes their existence to, I say! None! They get nothing!

As an aside, I realize people in this thead are asking this mostly rhetorically, but the game does provide a real, concrete answer to "why didn't Venat say anything" beyond her unconvincing mumbling about Hermes: she says straight out after said mumbling that her chosen course is not to stop Hermes's test, but to see mankind confront and pass it, to "prove" the strength and worth of life. The writing wants us to understand this as a brave and noble course, not a callous one. Of course, as far as I personally view it, I think another poster a while back framed it best when they described it as her choosing to throw away and otherwise gamble millions and billions of unknowing, unwilling lives she had no right to in a "philosophical pissing contest" with Hermes.

Venat's love of Life is true, genuine and zealous. Even her short story makes sure to highlight this, in her sheer giddiness about her research thesis about the inevitability of Life, if Existence. She just views Life as a holistic and abstract thing, as she described in her changed worldview in her speech on the bridge, and as a "force of nature" (per our Azem) would - and Meteion's report suggesting that Life is worthless, that the universe was empty, that an outcome was possible that people stopped valuing it properly (this, I'd guess, if I was trying to actually make a good faith effort to make heads or tails of her character, is why the Nibirun upset her so much more than any other possible Dead End described) truly disturbed her. If billions of tiny individual lives must suffer, die (and know?) to prove the overall value of Life as a unit and a concept, prove Meteion wrong, then so be it.

EDIT: Again, I would presume this is where the disconnect between the writers and the players chiefly lies. From the writers' perspective, this was a well-intended and sweet, if somewhat naive, message to the players merely using the game, world, and characters as a vehicle to tell us: "Look! Life is worth it, even if things are hard! Don't believe someone if they tell you to just give up and die! Let's affirm that life is worth it together!" However, the second you move from "this is a message from the devs to the players" and into the actual in-universe setting and logic, what the characters themselves are doing to, from their perspective, other living and breathing people, it becomes absolutely horrifying on several levels and really difficult for me to not describe as basically flat-out evil, if I'm being blunt.