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

[Lauront]

Only the Convocation was tempered, as a side-effect of the summoning due to the power that went into it, and even then, Emet-Selch could deviate from his original plan, where he deemed this to be appropriate. Elidibus was controlling the primal and emerged from him to mediate the dispute, so we can reasonably infer he knew what was happening with the souls inside of Zodiark, and may have even brought this into discussions between the ancients on that topic.

As for exchanging the problem? I don't think that'd necessarily be the case. The setting doesn't outright say it, but there does seem to be a differentiation in the souls it sticks in sapient races, like the ancients (to the point that even after thousands of years, we can reliably say the sundered are fragmented ancient souls), and those that go into animals and non-sapient monstrosities, which wouldn't have cultivated the notion of returning to the star as a yearning. So as an exchange of power so that the primal remains at full functionality, to liberate the souls of their brethren, it makes sense.

We need to recall Venat did not share the specifics of her concerns with them.