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

[Lauront]

I was under the impression according to Shadowbringers and Emet-Selch's explanation is that people weren't killed when the sundering happened, just their souls were split. All the current shards that happened right after had all the remaining people were identical in appearance/intelligence/ect (when he demonstrated on Ryne) but had forgotten about being long lived beings or about their past and whatnot and then they just died due to the normal things like happenings of war, sickness or old age. I don't see how that is "killing everyone."

What Venat did was the same exact thing as what God did when he cast Adam and Eve out of paradise for not learning and heeding His lessons. She tried reasoning with them and making them learn, they refused, so they were cast out of paradise (Unsundered world). Minfilia is akin to what happened to Jesus. God also flooded the entire world in what He deemed to be a greater good for the world. Yet I don't see people ranting about how God is evil for doing that.

I think you need to go re-watch that scene. He's not saying they're identical at all in that scene, and factually, they are not, across a number of different dimensions. Their lifespans alone are cut by a significant factor (nigh immortal to the much shorter sundered lifespans), which would've killed any ancients off at the time. If you don't see how that is "killing everyone", then I guess you won't see how, say, slowly poisoning everyone so as to cut their lifespans down is killing them either, because death doesn't occur right then and there. They did cover the aftermath of the Sundering in the Nier crossover, here. Likewise, the modern races evolved out of the fragmented ancients to adapt to their environments given their newfound frailties, as per the Q&A pre 6.1.

Regarding your second paragraph, there are plenty who do in fact argue that the biblical deity is malevolent, or at the least quite harsh, for that very reason, but Venat is no god - she is an ancient herself. What we were shown of her in that very loosely inspired by the facts, pity me scene is not her trying to 'reason' with her people (to what end? is it a time loop or not? would they be able to wield dynamis or not? what is her end game if they did listen?), but tone-deaf lecturing delivered to a people still grieving apocalyptic levels of destruction of their star, which required the sacrifice of 75% of their number to halt the apocalypse and restore their star to a functional point.

Again, what is the difference? It's okay for God to do it because He's a God? How do we know the Unsundered people aren't considered Gods in this story and she just happens to be one of them? They were creating life with just their wills and magic, just like a divine being would. That sounds pretty Godly to me. We don't know much about the ancients to deem whether or not they were Godly beings or not.

I'm just pointing out the hypocrisy of blaming Venat. If you wanna blame her, anyone who is religious needs to look to their own religious figures and well and question that.

You can direct that argument at any who are religious here, but it's not really on very solid grounds, not least of all because the god in question is, in relation to those he inflicts his decisions on, a higher being, and not just that, but the creator of all existence and life, both of which traits are relevant to its godhood and thus its perceived authority. The ancients may have many transcendent traits compared to humans, but she is one of them, they are still sufficiently human-like for us to be able to empathise with them and they did not see her as a/their god, let alone their creator; the latter two are are things she is emphatically not. So I am unclear on what 'hypocrisy' you're supposedly pointing out, even if someone is religious - which I am not; I thus have little interest in defending the biblical conception of god. Even so, trying to conflate her with the biblical god, a being which is not human at all, is just strange to me.