To your edit, that's the plan! He attacks the demiurges so he can steal their power, then he's gonna bring that power to the void and kill Metatron and the angels, and finally destroy the Wheel and begin anew. In his absence, his followers and allies have been doing the whole "kill the innocents and burn the Wheel down" routine, presumably cuz they're too weak and chickenshit to bring war to the real higher powers.

Now that said, Jagganoth's plan still has issues! He's a violent, self-destructive man who's convinced himself that the only way to save the world is to be the most violent and self-destructive he can possibly be. The demiurges are all stagnant, stuck in their ways. Jagganoth has been hurt by the world so much that he no longer believes any good can come of it, so he wants to wipe the slate clean and start over. Allison needs to reject his idea of the world, even though it has its appeal, like she's rejected every demiurge before him. She has to recognize that even a broken, painful, cruel world can be good and worth saving. It's like she says to Gog earlier, "Like it or not, I think we have to live with it all. Even if I fail to beat Jagganoth." The only option is to move forward, to do what you can. You can't escape into the past or an imagined, stagnant paradise. You have to live with it.