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

[Lauront]

I guess I could've phrased myself more clearly. What I am getting at is the way that Hydaelyn/Venat keep associating Meteion/Endsinger and the despair she brings with darkness. Not so much Zodiark, but on reflection, you'd have to forgive players who aren't as attentive to the lore as we are, for perhaps being confused when confronted with "The Eternal Darkness" within "The Dark Inside". This is not helped by Hydaelyn's codex later being added and referring to him rather uncharitably as the manifestation of an "ill-fated wish". Part of the issue is they're using the term in different contexts - one to refer to a type of energy, which Zodiark is made up of, and the other to signify negative concepts. By contrast, you have the pristine and angelic "Divine Light". With Zodiark I was getting more at his appearance, and it is relevant to bring it up in that context as well, because even though darkness-aspected beings tend to have a more demonic guise, it felt they went overboard with it in a way that wasn't really consistent with his statues or much of what we know about Amaurotine society. I did not dislike it, but it strongly pushed in the "big bad demon" direction, especially with the tentacles. With the codex in mind, I couldn't help but think they are trying to re-cast him as the embodiment of something bad, only moving the needle from darkness being inherently bad, to using the term to signify despair, and pushing him as the pathway towards the ancients' doom (the over-reliance, as you put it.)

And yes, on this:

I've come to the point where I prefer to see "gods" and "deities" in stories presented as actual nuanced characters and not just "Big Goods" to be obeyed and "Big Bads" to be slayed.

I am in firm agreement. Mostly because I do not like the whole "punch god" trope of JRPGs.