I'm so glad this expansion finally got back to the heart of the story. For so many years we lacked the most basic information on the origin of our enemies. Had the other ascians in the past been as open about their motives as Emet I may have sided with them. Sometimes when I'm depressed I think about real life as an ascian would, that there are so many problems in the world wouldn't it be convenient to raze it and begin anew (with the guiding hand of the intelligent elite survivors).
Even if ascians don't do the genocide thing, there would just be auto death and pain due to the affliction of mortality and aging. To restore a world of harmony and happiness, isn't it worth the cost? However... how do we know the rejoining would be a success? I may have missed something in the story; did they explain why there was an apocalypse with demons and rivers of blood? That whole thing could just occur again after the rejoining so it's unfortunately not very convincing to back the ascian plan of a better world. The need for primals could just arise all over again and end up dividing the world into reflections again lol.