Endwalker's message (spoilers!)

[KizuyaKatogami]

Zodiark was their solution, and a solution that beget suffering whilst not solving the issue. It's tragic, but it is meant to be so. Furthermore, upon his defeat all ancients trapped within and the unsundered are implied to have been freed of tempering as Zodiark's tempering was different. Although these were souls rather than physical forms.

Zodiark saved them and the world. Were it not for him the world wouldn’t exist. I think the blame falls more upon the likes of Venat whom, if she had informed Hades and Hythlodaeus of the issues, Zodiark would’ve given them enough time to presumably solve the issue of Meteion. I guess you can argue that with Zodiark saving the world he in doing so caused suffering that otherwise wouldn’t exist since everyone would be dead but that’s essentially Meteion’s mindset so

[RitsukoSonoda]

Zodiark saved them and the world. Were it not for him the world wouldn’t exist. I think the blame falls more upon the likes of Venat whom, if she had informed Hades and Hythlodaeus of the issues, Zodiark would’ve given them enough time to presumably solve the issue of Meteion. I guess you can argue that with Zodiark saving the world he in doing so caused suffering that otherwise wouldn’t exist since everyone would be dead but that’s essentially Meteion’s mindset so

It's also possible that Zodiark would have lead to the extinction of the ancients given that more of them were basically feeding themselves to it in hopes it would return the world to how it was before the end of days. They basically stopped looking to the future and wished to return to the past. Which by retaining the knowledge of Meteion's reports was a mindset that lead to the end of other worlds. So even if Zodiark had successfully restored the world to how it was before the end of days, the mindset created by the event would have likely lead to an end similar to other worlds meteion visited had experienced. Also given emet selch's initial reaction when the WoL informed them of the end of days it was likely reasoned providing that info after the memory wipe when no physical evidence was available wouldn't have accomplished anything.

[Vahlnir]

Zodiark saved them and the world. Were it not for him the world wouldn’t exist. I think the blame falls more upon the likes of Venat whom, if she had informed Hades and Hythlodaeus of the issues, Zodiark would’ve given them enough time to presumably solve the issue of Meteion. I guess you can argue that with Zodiark saving the world he in doing so caused suffering that otherwise wouldn’t exist since everyone would be dead but that’s essentially Meteion’s mindset so

I think a lot of it came down to Venat not wanting to create a time paradox of some kind. In her eyes, the time of the Ancients was coming to a close. Even if she had come forward with the information she had available, her peers might have thought their civilization too big to fail and ignored her. That and Meteion was hanging out at the edge of the known universe, where she couldn't be reached (well, back then anyway). And the Final Days hit them pretty soon after she vanished, so they didn't have time to construct a means to reach her. Venat was looking to preserve a future that could still be saved.

[EaraGrace]

Zodiark saved them and the world. Were it not for him the world wouldn’t exist. I think the blame falls more upon the likes of Venat whom, if she had informed Hades and Hythlodaeus of the issues, Zodiark would’ve given them enough time to presumably solve the issue of Meteion. I guess you can argue that with Zodiark saving the world he in doing so caused suffering that otherwise wouldn’t exist since everyone would be dead but that’s essentially Meteion’s mindset so

The point of Venats plan, a plan Emet and Hythlo agree with once they remember everything, are that relying on a deity to solve all your problems will at the end be self defeating, and that what is needed is a response to despair. You inevitably will have to face suffering, and the Ancients, who have shown no willingness to accept that, would fail. Zodiark doesn’t solve the problem, he buys time.