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

[dapperfaffer]

Except we’re later told that’s not exactly what it was. Venat’s whole thing was she didn’t think the Ancients could overcome despair/suffering and defeat Meteion. She knew Zodiark wasn’t a permanent solution, we’re shown this in Anamnesis. However the problem here is she didn’t even give the ancients a valid chance. She gave up on them in favor of someone she had only just met. We know they can manipulate Dynamis, we know that she could in some way get through to Emet. She just chose not to. If they had at least had her mind wiped then her actions and the sundering would make a bit more sense as at that point it would be more an act of pure desperation and unknowingness.

She didn't know it wasn't a permanent solution, their is no way for her to know that in any other timeline than post WoL and even then she still wouldn't know because the post WoL events never unfolded, the pre WoL events did. What she acted upon was the possibility that Zodiark would fail to stop the Final Days and they would all be doomed, and in her cutscene she specifically says suffering is good to the guy begging to Zodiark to return to them what was being destroyed. And then she sundered Zodiark, and walked through a black time tunnel.
When you first get to Elpis Venat recognizes her marking you with her magicks and says something about a familiar presence, then when she meets WoL she recognizes it again and points out that its her magick in front of Hydro and Emet. She trusts the WoL because she recognizes her own power in them. Which is also why in prior expacs some Ascians refer to the WoL as Azem.
Also, not everyone can manipulate Dynamis and seems to be something rare or somewhat unique to Hermes. Dynamis was a little known thing as is explained by Hermes in regards to one of the conversations involving Meteion.

But he's not even correct on that point. They weren't indifferent about it - we see that in sidequests in Elpis. His problem was that they applied a standard at all, i.e. permitting creations to persist only when they contributed to the betterment of the star. We see this with the lykaones, where he wishes them to live even if they were detrimental to the star's ecological balance. These are just arcane constructs in the end (even more abundantly clear with the sprites, where he discussed their impetus to exist), which might get a soul if they satisfy the star's criteria for doing so, and even then it'd just upgrade them to the equivalent of animals or monsters. Beings the sundered kill without a second thought, much as they send their own arcane constructs, like egi, to die for them. Moreover, he also had a problem with his mentor's decision to return to the star. None of what he said is going to stop us from going on hunt trains to reap souls to fuel our next relic, for example... His real beef was that existence itself ultimately entailed death. In the end, that entire line of thinking is discarded by Venat who is only concerned about answering his question for the purpose of surviving to drive back Meteion. He is little more than your typical pathological "empath" with a sadistic streak.

Hermes doesn't need to be correct. He just needs to have a motivation for his actions. Motives that span Hermes, Amon, and Fandaniel as characters.