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

[Rulakir]

Also, Midgarsomr and Tiamat himselfs hint the possibility they had a hand in Dragonsong War starting in Azys Lla as they point them to be the root of the miseries. Not to mention, we see several instance of Ascian causing disgraces left and right, specially in ARR. Also, Garlean and Allag catastrophes were full within the Ascian plans and the Ascian themselves helped them to it (Dalamud is a pretty good reminder for both cases). Also, Emet-Selch is very explicit in saying "the remaining habitants of the Source". That really isn't open to any interpretation and it being "non-Amaurotian" REALLY doesn't soften the blow of, you know, commiting more genocide for their egotistical objectives.

The events in Meracydia aren't linked to the Dragonsong War. If you have evidence the Ascians were involved in telling Thordan I to slaughter Ratatoskr and devour her eyes or telling Nidhogg to enact 1k years' worth of revenge upon Ishgardians for it, then by all means.

It's not meant to soften the blow, it's meant to clarify. I'll also say again, rejoinings wouldn't have been a thing without the sundering in the first place.

She was not suddenly anti-sacrifice she opposed the idea of summoning Zodiark from the start.

I'm going to need a source for this because Venat had no plan that didn't involve Zodiark's aetherial barrier buying them time.

Her faith in mankind was finally rewarded in the end as we became strong enough to stop Meteon without her or Zordiark.

Ah, no. The day was barely won by the WoL who had been groomed for it from the start and given every tool past, present, and future to ensure success, which included the assistance of the unsundered. (Noting that were it not for Emet's sentimentality he would've likely killed the WoL on the spot on the First, so the WoL also had to be a reincarnated Azem for this to play out as well.) Mankind without the WoL and their links to the unsundered absolutely fails to defeat Meteion.