You don't get to have your cake and eat it too, demanding the hard evidence for any kind of alternative to the Sundering, and then base the entirety of your previous post decrying their society as "there probably was agony and strife around, we just didn't see it!" Obviously their society was not perfect, they have struggles in their lives, but I say more power to them then, it humanizes them more and we've just recently learned that being actually perfect is bad. Come on, even Hermes, the #1 Ancient hater says they go out of their way to make sure their creations do not suffer unduly. It's just that wasn't enough for him, because he knew they sensed their impending demise. I get you're searching for ammo where there is largely none to suit your narrative, but there has to be something better to use than that.
At the end of it all, and this is now further supported by this Omega quest, all of this is predicated on belief. Even the devs told us that Venat was acting according to her 'beliefs.' The Watcher here just told us that he 'believed' the Ancients would eventually fall, and that the WoL may very well disagree with this notion. There is nothing objectively correct about her decision, and thus people are free to speculate unaddressed alternatives all they like, because they really should have been addressed. They're not doing any greater amount of filling-in-holes with fanfiction than you are. Me, I'm content to just call it questionable writing, that so many things need fanon explanations on forums like this.
But speaking of a lack of evidence, Hermes is never accredited with Zodiark's construction. Never. Not one time. If he was at all vital to Zodiark's innerworkings, that is something that needs a thorough pointing out, because from where I'm sitting, he has no further involvement than any other Convocation member. A primal that is using an aether shield does not need a dynamis expert. All of his 'vital' knowledge of the root cause of the Final Days only remains vital because Venat chooses to keep under wraps that she learned basically everything valuable from him secondhand already. To be honest though, this is all from the 'rushing you out of Elpis' epilogue scene that I already have several very strong issues with.
But ahh, its been this long and people are still taking Emet-selch's 'our methods' line as him saying 'there was nothing our society ever could have done to combat this threat.' You know, the society that he still believes is superior and just got finished telling Meteion his answer as a representative of, for the sake of 'all lives, past and present.' That totally makes sense. Sure, let's just extrapolate that instead of taking it as him meaning, far more sensibly, the Ascians and the Rejoinings.