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

[Lauront]

I am very much appreciative of the information given and am learning quite a bit. The only part that still confuses me is the constant mention of "prayer" in regards to Zodiark. The dialogue of Emet-Selch in the Ravel's Keep dungeon holds Zodiark in much higher regard than a creation or tool to stop the Final Days, but much more of a deity. Unsure if I am reading into it wrong, but seeing Zodiark referred to as "Him" with a capital "H" like some religions do, saying "His grace". "A savior mighty and magnificent, deserving of reverence and gratitude" really doesn't sound like something the Emet we meet on Elpis would say, which is why I am still locked on Zodiarks tempering of others. Though to be fair he also mentions how "they fought, and they fought, and they fought." which does not appear to be what happens in the cutscene we see, so both could be explained by a change in story direction.

Reading further into the plan with Zodiark though(correct me if I am wrong), it seems on the final step they were planning on sacrificing the new life brought back to Etheirys with the power of Zodiark to bring back the souls of the Ancients used to summon Zodiark initially? If so, perhaps it was that choice of sacrificing other life of Etheirys for the sake of the Ancients that both Venat(the previous Azem) and the current Azem disagreed with, both being the "Traveler" and holding life outside of the Ancients in much higher regard? Though I could be missing information in this logic.

No, the final stage (and I am filling in some gaps here on what it was because the story is very vague on this life besides possessing souls; nonetheless, I think the JP version of the Hyth text is instructive) by all appearances would involve creations similar to those in Elpis. We know from the quests in Elpis (but also Emet-Selch's short story) that creations meeting the right criteria would qualify for souls from the star (the star itself spawns these), appropriate to the type of being it is, and so you'd get animal and plant life - for creations which do not qualify, they're essentially arcane entities. So when the story uses the term "life", it means creations qualifying for a soul, which the star itself bestows upon them. It is a very broad spectrum of things, mostly consisting of plant and animal life, and as KageTokage mentioned, precursors to the sort of beings comprising the beast tribes.

Current Azem opposed the summoning of Zodiark altogether, but the reasons are not given. It's possible that Venat knew what was to come and nudged them to do that without offering them any reasons and that their trust in her as a mentor led to them simply taking her word for it, hence it seeming so capricious to the remaining Convocation. The sacrifices are not given as the reason for it as their departure pre-dated his summoning.

As for Venat, the rationale given both by her and in the recent Q&A the devs did is avoiding the fate of the Plenty. Preventing the sacrifices is only a means to that end, i.e. for the ancients to desist in their efforts to revive their civilisation. If you read the sources I provided, you will see that there is very little moral condemnation discussed about the sacrifices in the scene in Anamnesis Anyder, and she even states that the Convocation was doing what it thought best to secure their star's future. The exhortation to hand over the star to the new life all seems to revolve around stopping the ancients from restoring their people and zooming ahead (in her view) to the Plenty's fate.

Just one final point - Zodiark very much is deemed to be a god, but the ancients - including Emet - see him as a manmade one. Likewise, Hydaelyn is referred to as an all-powerful being by Y'shtola, and refers to herself as a "supreme deity". This all comes down to their sheer power, rather than tempering, per se. Lahabrea and Nabriales took it a step further with their zeal and that I believe is why they brought it up - Lahabrea in particular let his identity fade through extensive body-hopping, and so the idea seems to be he was changed by it unlike Hades. Elidibus sustained memory loss but his guiding duty, stemming from the Convocation, appeared to at least allow him to retain enough of his identity to avoid going the way Lahabrea did.