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

[Velnora]

I mean, the catalyst for the Final Days in their time is one and the same as the one in the Sundereds' time. Difference between the two episodes is, initially, they never pinpointed the actual reason and only Venat (presumably others she informed) knew of the actual source of the problem and Zodiark, despite being a God to rewrite the laws of reality and to bring salvation, ultimately acted more like an aetherial dam for the torrential rivers of Dynamis coming from the Ultima Thule (and, as a result, providing a bandaid solution for temporary relief). His presence was also to strengthen the waning celestial aetherial currents, as originally Fandaniel assumed that those weaker spots were part of the reason behind why things were going to shit.

Ancients were too aetherially dense for the Dynamis to interfere directly with their physical being, so instead their creations - which are made up of a fraction of their aetherial energy - began to turn instead. Whereas, for sundered souls, their aetherial density isn't enough to purely ward off Dynamis (and also leads into the ability to more easily directly channel/manipulate dynamis, ie: Limit Break, Dynamis Dice as gameplay mechanics.)

Dynamis itself just energy affected by emotion, and emotions cover the entire emotional spectrum. It, itself, doesn't have a motive unless it's harnessed by someone who does (the Meteia).

The WoL/Scions removed the catalyst for the Final Days (the Meteia and the overwhelming sorrow/despair/etc... they hoarded for millenia), and so the Final Days ceases.

But if it doesn't have a motive, then it shouldn't affect Meteia. Dynamis is stupid.

[Alaray]

But if it doesn't have a motive, then it shouldn't affect Meteia. Dynamis is stupid.

Dynamis isn't what affected them, though -- the Meteia are, in FFXIV's version of the word, entelechies, which are basically empaths in this case. Once so many Meteia encountered so many incredibly dense, negative emotions from those civilizations they watched fall/die/etc... those feelings became a part of their emotional state, a constant burden of sorrow born from the ends of thousands of worlds. They could no longer separate their ontological selves from the massive tsunami of these emotions (and part of this is a bit of a design flaw, since they /are/ made primarily from Dynamis, which would mean their Dynamis would change to be aspected to these emotions as they continuously encounter them). To where, their thought went to "everything is destined to die, and so everyone is destined to suffer. The only way to remove the suffering, is to kill everything" (mirroring the conclusions of the dead civilizations, which were conclusions born from the same source of emotional distress) and from there, they harnessed the external energies of Dynamis that was then heavily infused with the sorrow of thousands, thousands of civilizations'. Dynamis is an energy affected by emotion, the Meteia harnessed it with a particular emotional drive and a particular motive in mind.

The raw, conscious emotions affect entelechies (the flower turning black with Hermes and you), dynamis is just an energy that's a blank slate until someone harnesses it with their own emotions (be it Sorrow, as seen from the Meteia, or Conviction, as seen when you LB3, or a mixture of Desperation, Conviction and Will -- like when Elidibus LB1/2/3/4's. Dynamis isn't /always/ sorrow).

[Velnora]

Dynamis isn't what affected them, though -- the Meteia are, in FFXIV's version of the word, entelechies, which are basically empaths in this case. Once so many Meteia encountered so many incredibly dense, negative emotions from those civilizations they watched fall/die/etc... those feelings became a part of their emotional state, a constant burden of sorrow born from the ends of thousands of worlds. They could no longer separate their ontological selves from the massive tsunami of these emotions (and part of this is a bit of a design flaw, since they /are/ made primarily from Dynamis, which would mean their Dynamis would change to be aspected to these emotions as they continuously encounter them). To where, their thought went to "everything is destined to die, and so everyone is destined to suffer. The only way to remove the suffering, is to kill everything" (mirroring the conclusions of the dead civilizations, which were conclusions born from the same source of emotional distress) and from there, they harnessed the external energies of Dynamis that was then heavily infused with the sorrow of thousands, thousands of civilizations'. Dynamis is an energy affected by emotion, the Meteia harnessed it with a particular emotional drive and a particular motive in mind.

The raw, conscious emotions affect entelechies (the flower turning black with Hermes and you), dynamis is just an energy that's a blank slate until someone harnesses it with their own emotions (be it Sorrow, as seen from the Meteia, or Conviction, as seen when you LB3, or a mixture of Desperation, Conviction and Will -- like when Elidibus LB1/2/3/4's. Dynamis isn't /always/ sorrow).

That all sounds like something that shouldn't have been introduced in the second to last zone, lol.

[Alaray]

That all sounds like something that shouldn't have been introduced in the second to last zone, lol.

I kinda do agree in some ways, where the formal explanation felt a bit sudden initially (more in a "oh, it's introduced and fully explained /this/ expansion"). Though, Nidhana mentions "Akasa" which is a word for Dynamis as understood (very lightly) by the present, sundered world (and this is introduced at the tail end of... I believe after Zot, when leaving Thavnair -- which is roughly where I went to "I assume Akasa, an emotional energy, has something to do with the core plot"). There are other little bits here and there that reference Dynamis, though the vast majority of people going through a story probably wouldn't notice since they're very off to the side (ie: Dynamis Dice was introduced in Shadowbringers, as part of the Bozja content and, even there, it's just an item that has a chance to randomly roll things like Healer LB3 or Doom) or the way Limit Break plays into it (which usually reads something like "Breaking the Bounds of Your Limits" which can be vague, though there were people thinking it was related to a different type of energy for a while, but it's a very small and easy to miss thing since on the surface one can just think "oh, breaking normal mortal limits = using more aether than usually possible").

Song of Oblivion was referenced back in Stormblood, during the Omega Raids I think.

There are bits speckled in a long time back, but they're really small and incredibly easy bits to miss since they're not really pointed out in the MSQ itself.