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

[Nilroreo]

I sometimes wonder if they were going to go with a Lavos-style villain as the big bad behind everything......then one day Ishikawa was going for a walk in a park and saw a blue bird fly by and an idea suddenly struck her: "wouldn't be a cool idea to make a cute little bird the big baddie?" and just completely derailed the original idea and that's how we got Meteion and why Meteion doesn't feel like she was originally what they had intended.

I was initially under the impression that this was going to be the case based on how one npc in particular describes the event.

'Tis said it starts suddenly, a cacophonous keening from beneath the earth. The sound distorts all living things within earshot, and wrests from us control of our creation magicks.

None can point to the source of the phenomenon. 'Tis as if the star itself has fallen ill─as if a force inimical to life now festers and spreads.