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

[Atelier-Bagur]

It isn't necessarily Venat that's the problem to most of the character's detractors. Omnicide is a very common trope in video games, after all. The real issue is a combination of the narrative treating the act far too lightly and the characters within said narrative being perfectly fine with all of it. What we, the players, were expected to feel about that character does not, in the opinion of many, line up with what we were shown. The omnicide, all the deceptions, withholding so much key information from the Convocation, not bothering to tell the people she sacrificed to become Hydaelyn their souls would be consumed, etc. would all be considered highly dubious actions individually, and she was written to have done all these things and more.

Venat is fine. The fact the character's rather horrendous actions are just hand waved... well, that's questionable at best. To top it off, there's a portion of the player-base that just wants to outright deny the character as having committed any wrongdoing. As you might imagine, these rather outspoken individuals have managed to rather thoroughly stoke the ire people that aren't so keen on calling Venat a hero. Tends to make the debates devolve into pointless arguments and wildly unfounded suppositions.

Again where are the direct sources of her actually letting her own followers be out of the loop for the summoning. Wouldnt the Ancients already know that fact when the same wanted to consume souls to summon Zodiark? Also the fact that she even had a group of her own kinda goes against the idea that she never told anybody the truth of what happened.

Im not trying to argue that Venat was this perfect angel of a character; she clearly wasnt and the story itself already shows you to not be some mindless worshipper befitting of primals indoctrination. But the things that people are arguing here about her feels like a long contrived stretch based on what was narratively presented. Its akin to the whole "ARR Gaius was right" debate where people also try to weirdly stretch that he was justified in his actions. People read shit in this game a bit too much

[KageTokage]

The "Venat allowed the Rejoinings to happen" doesn't really hold water. We know she actively worked to stop the First from being destroyed. We also know that she was creating Warriors of Light throughout the eons. If you want to criticize her for failing to stop them, that's fine, but this implication that she just sat around eating grapes until Rejoining #7 doesn't work.

Preventing that rejoining was also crucial to allowing the critical events involving Emet-Selch and Elidibus to play out so that the causal loop could be maintained.

It's really hard not to view at minimum everything surrounding the First as orchestrated considering that she knew leaving Ardbert lingering behind as a shadow was going to be necessary for our success.

Again where are the direct sources of her actually letting her own followers be out of the loop for the summoning. Wouldnt the Ancients already know that fact when the same wanted to consume souls to summon Zodiark? Also the fact that she even had a group of her own kinda goes against the idea that she never told anybody the truth of what happened.

The short story about the Watcher mentions that they did know that their sacrifice for the summoning would have to be "absolute" and remove them from the cycle entirely.

It does not specify what she told them, though, only that "precious little" about the future was disclosed. Whether that includes the Sundering or not is anyone's guess, though given that we're due for another talk with the Watcher in Myths, it wouldn't surprise me if they decided to fill in some more blanks...though honestly, them knowing and being perfectly okay with it still wouldn't make me feel much better considering that they were willing to condemn Hythlodaeus and the other sacrificed to a potentially indefinite purgatory for the sake of their ideals.

[Absimiliard]

Again where are the direct sources of her actually letting her own followers be out of the loop for the summoning. Wouldnt the Ancients already know that fact when the same wanted to consume souls to summon Zodiark? Also the fact that she even had a group of her own kinda goes against the idea that she never told anybody the truth of what happened.

In-game text, developer commentary, and peripherals cover these things. One such instance of an interaction between Venat and her followers, which is to have taken place immediately prior to the Hydaelyn summoning, has one of them talking about the next time they meet. It's made even more apparent in the JP text, wherein the conversation has even less of a "this isn't our last goodbye" tone and leans much more into "we will definitely see you again" tone based on the selected wording.

Incidentally, Zodiark at no point consumed the souls being used to summon him. In fact, one of the primal's directives was to safeguard those souls until they could be resurrected. Every soul sacrificed to Zodiark was still "alive" within the dark primal until the moment of its destruction. The Hydaelyn summoning, on the other hand, completely used the souls up. We're given to understand the limited number of sacrifices available to Venat at the time made this an inevitability - if not at the moment of summoning, then definitely when she used her newfound power to its fullest to sunder the world. All that remains within Hydaelyn by the time she tests the WoL is her own soul and enough stockpiled aether for one last confrontation at the height of her power, after which her own soul's aether is left depleted. Using up all the gas in the tank means your soul gets destroyed. You don't get an afterlife, and you don't get to reincarnate; you are unmade forever.