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

[Absimiliard]

Elidibus did say "Yet even should you manage to interact with others, you will be unable to effect meaningful change."
Meaning he hard confirms that whatever we do in Elpis has no severe implications in the course of history, so we didn't really "intervene", we were just present as the events unfolded.

Bear in mind the state Elidibus sends the WoL to Elipis in. You're not even a phantom at that point, able to observe but do naught else. Emet-Selch's gift of aether amends this problem in its entirely. Through this you are in fact able to effect meaningful change.

As to your point from a prior post; this type of temporal paradox has no beginning and no end for all practical purposes. Venat is reliant on information received from the WoL to act in a manner that will preserve the timeline as it will be, but said timeline must exist for Venat to receive this information in the first place. If you've heard the phrase "the serpent eats its tail," this is one of those times you'd apply it. That aside, the implications of the WoL's death in G'raha's timeline probably weren't accounted for by the writers. Were I to theorize, however, I would say the existence of the tangential timeline the game presently takes place in was always meant to be. You might also consider how the original and current timelines presumably run identical until the exact moment they split, which would mean the WoL from the deviant timeline going back to Elpis would spare the other from preemptive deletion.