Let's play a game: Save the Ancients!

[Yuella]

Venat did tell them how to beat the Final Days in that lengthy cutscene

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Venat
No, my friends. Suffering exists, and we cannot pretend otherwise.

No civilization, however great, could eliminate it. If we would live, we must accept it as our constant companion.
Let us not seek to forget this tragedy. Let us carry it in our hearts, that we may grow stronger and know true happiness.

Bitter Ancient
We can't accept it! We won't accept it! It will be ours again—a world free of sorrow!

Venat
No, it will not, for there has ever been sorrow. Mankind was but spared its biting sting for a time.

So please, open your eyes. To try and reclaim those lives we lost by sacrificing yet more isn't wisdom. It is weakness.
No paradise is without its shadows. If we cannot accept this truth and learn from our pain, then our plight shall be repeated.
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Stopping that particular Final Days would not stop another Athena or Hermes from doing the same thing again 1000, 10000 or 100000 years in the future if they never learn how to accept sufferings. This is the main point of the story (the details don't matter). There's no such thing as a perfect society (otherwise people like Athena or Hermes would not exist) and they have to learn accepting imperfection as part of their society instead of declaring every imperfect things or beings a failure immediately. Maybe there's a slight flaw in the writing where they didn't hammer this point well enough but the main idea is solid.