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

[Seraphor]

Venat does not want the Ancients to rebuild their society and save those trapped within Zodiark and unable to re-enter the aetherial sea. She sees these acts as a rejection of suffering and believes Ancient society should move forward as is.

Citation needed. You're inferring an intent that isn't stated in the content.

I come back to this:

On a funamental level, the Unsundered are incapable of resisting the final days, due to their aetheric density and lack of ability to control Dynamis.
Only fragmented beings have the potential to develop the resistance to the effects of Dynamis, by virtue of learning to cope with suffering.
Unsundered = doomed to die, no alternatives. Sundered = potential to survive.

Period. Anything more than this is conjecture and whataboutism. This is what the story (maybe poorly) tries to communicate.

This is the basis of all the events that led up to and followed the Sundering. It's survival.

The concepts from Buddhism and Utopia serve a philosophical and literary justification for it.

You're all looking at it backwards.