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

[SaitoHikari]

That's the thing.

Endwalker was originally intended to be two expansions as per some past interviews, with Garlemald slated as being the endpoint for the first of them, meaning the tower business was supposed to be a much more lasting threat then it was.

That would've presumably left the Final Days with an expansion to itself and a lot more time for the subplots surrounding it to develop.

Good lord, this explains a lot. You can basically tell this was a consequence of the writers writing themselves into a corner with Varis dying and Zenos basically hijacking the plot from the Garlean side of the story.