Endwalker was a great mess(SPOILERS)

[Lauront]

As for Combating Meteion, that was NOT in the Convocation's mind at all. Remember, their goal was to reclaim their paradise.

Because they didn't know the cause. Hence, people are asking why, knowing what we do of time travel splitting into AUs, she did not divulge it. His point is predicated on her sharing that knowledge. Also, leaving aside the speculative parts over whether Kairos would render the Echo unable to access those memories, Hythlodaeus had already meant to ask about the companion that had joined him and Emet during those days. She had potential in-roads. She just chose not to utilise them. The real reason here is the writers wanted to wrap up the story, not create a rationale for an AU, and searching for reasons beyond that is likely to prove a sterile activity. It's just unfortunate that they chose such a convoluted way to do it.

It wasn't to move forward. The events that caused the Final Days made them lose hope. Venat only decided to sunder the world after she realized there was no way to get the Ancients to stop sacrificing themselves to Zodiark to restore their world.

Citation needed. I'll save you time and tell you that this isn't quite correct. They were not committed to on-going sacrifices. The first set had driven back the Final Days, and the second set re-established the star's functionality; the final set was to release the ancients within Zodiark and restore them. A possible motive being that they placed value on being able to one day return to the star, and it's not clear they'd be able to do that while in Zodiark. Her reason for disagreement with the Convocation was that she and her faction preferred the new life (unspecified in nature, therefore could just as easily be the sort of creatures being created in Elpis as we now know these could gain souls subject to the right conditions) over her own people as inheritors of the star.