After all we learned in Endwalker I honestly feel joining Emet Selch would have resulted in a far better result.
We learned a lot of things in endwalker, dispelled many false beliefs about Zodiarc and the Ascians.
-We learn that summoning being at the level of Zodiarc does not mean tempering similar to eorzean primals, that was simply an addition to the summoning spell, for beings such as zordiarc you still feel a "tug" which can be described as a form of tempering but nothing like what we expect from the average tempered individual, Emet Selch himself was evidence of that after all since shb.
-Zodiarc was not an evil cunning manipulative entity, like all primals he was a tool serving a function, most should have known that since Shb. Meaning as long as he existed, he would have kept the celestial currents going protecting eithyris from the song of oblivion giving the convocation enough time to figure out what to do.
-The souls that were sacrificed to summon Zodiarc where still around, within Zodiarc, so we know absolutely know Zodiarc could bring them back if additional sacrifices were given. And then the WoL goes in and kills them all by killing Zodiarc(The good guy btw)
-We know that the concept of dynamis already existed even though not as widely known, and they also knew that the events of the final days first appeared in areas where the celestial currents were weakest, given time it only makes sense it would have been figured out.
So by joining Emet Selch and rejoining all the shards Zodiarc would have been unleashed, as long as he lived the celestial currents would keep running and keep Eithyris protected.
Hydaelin would be unable to win and I believe since she still cared, she would try to explain the nature of the threat before her demise, leaving the rest to you and Emet with Zodiarc as our available tool.
We could have brought back the original world after Meiteion was dealt with, the objectively better world with beings who literally wield the power of creation and are focusing on creating a better world.
Still, I do feel the problem itself could have been avoided had Venat reminded Emet Selch of what happened, just imagine that situation.
They knew what caused the final days, not only a more specific solution could have been created by finding a way to quicken the celestial currents (Since zodiarc was summoned to fix a problem they couldnt figure out) but even with Zodiarc, his existence would allow for many many years to figure out a solution, and with the very power of creation and a huge list of creative concepts it is more than likely that a solution would have been figured out.
Though at the same time I do understand Venat's point, she show how weak and reliant the ancients had become on their powers, and how a simple tragedy broke them. Understandably repulsive.
But killing them off was not the right solution, not only she could have used that as a lesson for a better future where a degree of suffering is ever present, likely through the creation of a concept with such a purpose, it would have strengthened and made eithyris better which was the core value of Ascians.
Many ancients might have fallen to true despair and become paralyzed, Emet selch and most of the convocation were clearly not like that, the Ascians even after knowing "True despair" clearly were able to keep going and focus on whatever needs to be done to bring back the original world, the better world. In short, Hades did not deserve this!