In the end, I was just disappointed that you couldn't tell Venat, "No. What you're saying sounds like a terrible idea. I don't care if Fandaniel played a crucial role in forestalling the Final Days on my timeline. In this timeline, you have a chance to do something about it. Tell the damn Convocation.
"As a friend of mine once said, 'This tragedy, greater than even the Seventh Umbral Calamity, must be undone. If history must be unwritten, let it be unwritten.'"
My theory is that this (and many other problems of the EW plot) center on the fact that the writers wanted to assure the player that the current world is "stronger", with the implication that (like another poster here tried to argue) that "death is necessary" or that tragedy always preludes a brighter tomorrow. (The Ultima Thule song, "Close in the Distance" is all about that concept.) "Even in the face of despair, grow stronger and never stop hoping for a brighter tomorrow" is the story's answer to the question of inevitable oblivion.
However, that argument wouldn't work if what we knew about the Ancients as of ShB was true. They and their society were presented as objectively better than the modern day. They were wiser, more advanced, more powerful, more long-lived and seemingly (based on how they treat you in Amaurot as well as how Emet-Selch describes their willingness to sacrifice themselves for their brethren) more benevolent. If EW had kept that theme, then the argument of "tragedy leads to strength and a brighter tomorrow" would have fallen flat, because the modern races are flat out weaker and living in a worse world than the Ancients ever did. (Granted, it did anyway, but not for lack of the writers trying otherwise.)
So they decided to go with the argument that the Ancients were "decadent" and that they "had to die" so that the younger races would be stronger and be able to fight for the "brighter tomorrow". However, they also didn't want to commit too much to making the Ancients complete jerkwads, because then it would make their beloved Emet-Selch (who they now intend to milk for fanservice) retroactively seem like a deluded idiot in Shadowbringers. Imagine trying to replay Shadowbringers and listen to Emet-Selch talk about the utopia of Amaurot when we go there and they're, like, grinding screaming Lalafells into their coffee or something. Thus, they had to try to make the Ancients "bad...but not TOO bad" which results in the complete dumpster fire that was the Elpis storyline.