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

[CrownySuccubus]

The result is accounted for in her action, but the immediate purpose was to stop the Ancients. The rest follows afterward. Like I said, an action does not have to have only a singular purpose.

*sigh*

Venat sunders the world to permanently remove the Ancients' ability to go back to their perfect world so that mankind will never again know the paradise they once had. Again, she is VERY clear that this is why she is sundering the world.

If true, then the idea of staying on the planet would be pointless, so I don't think that is true.

The fact the death of the Star is inevitable, with or without the Final Days, is literally the entire point of Endwalker.

Weakening Zodiark was to stop him from being used by the Ancients. If the Ancients had stopped after the first or even second sacrifice, there would not be a sundering.

No, sundering the world was specifically to remove mankind's ability to reclaim their paradise. I repeat. Venat is very clear that this is the reason she sundered the planet.

Loss of creation magic is not necessarily an injury that I would equate to permanently having a broken arm.

Yes it the hell is.

Creation magic was the foremost power of an Ancient. It was what their entire lives, abilities and survival depended upon. When you go to phantom Amaurot in ShB, the Ancient shades there are aghast that you cannot do it, wondering how the hell you even get by in life.

Using creation magic was as fundamental to an Ancient as a human's ability to walk. When she sunders the world, Venat even calls it removing mankind's wings. And guess what, if you permanently remove a bird's ability to fly, then that is an injury.