Endwalker's message (spoilers!)

[Caurcas]

How so? The final days wasn’t really their own doing, and they were suffering trying to bring back their loved ones. As we know, a primal being slayed doesn’t untemper someone so presumably the sundered ascians are still tempered. If you mean the souls within him then yes but i meant moreso the ancients as a whole.

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.

[Garnetiferous]

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.

What you're forgetting is that without the Ancients summoning Zodiark, the world dies in the first final days. The issue was more that after they summoned Zodiark to stop the final days and fix the world to the point where it was habitable again, the ancients wanted to sacrifice more to bring back the old days of paradise. Which is why Venat stepped in. But the ancients can't really be faulted for summoning Zodiark in the first place. It was probably the only solution they had at the time against an energy they didn't understand and didn't have time to learn to understand.