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

[Rulakir]

From that model we can deduce that even if we "change" the fate of the ancients, we are only creating a second branch of time. Our original timeline and all of the suffering within it will not be erased, but we may not be able to get back there to save it.

I think I see what you're saying. Basically, the Elpis we visited could have branched into an alternate timeline we don't know about if that Venat had at any point changed her mind but, regardless, the Venat in our timeline ended up following the roadmap of the future we told her about to the letter?

The only problem is still the 8UC. Everything in that timeline happens the same as ours, however, the WoL is killed by Black Rose before they could journey to Elpis. Venat doing everything exactly the same regardless of the WoL's interference requires a substantial suspension of disbelief. The only work around I can think of is a future reincarnation of the WoL doing it and there are a lot of issues with that too.

It did work with Emet-Selch first.

True. It's like Ishikawa said in the Famitsu interview, Emet's motives were more sympathetic. The unsundered were put in the position of victims, whereas both Hermes and Venat were always the aggressors.