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

[Cassar]

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 is what kept it going. It was probably always meant to be that way. 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 offshoot going back to Elpis would spare the other from preemptive deletion.

Right but when Elidibus says that, he says it right after mentioning that you wouldn't be able to interact with anyone (I probably should've typed the whole quote) so, in my interpretation, what he meant was:
"Oh I'll send you in a state in which you won't be able to interact with anyone... However if, for some unknown reason, you are able to interact with anyone (which we do), you still won't be able to effect any changes"

And yeah, I mostly agree with the second paragraph of your post but I really do think that everything that happened in Elpis would've happened regardless of our intervention, and I find it hard to believe the writes wouldn't account for something so trivial such as the death of the WoL in Graha's timeline, which they made such a big deal about in Shadowbringers