@NikaInParis honestly it's kinda crazy how easily Greg could have fixed this harmony bullshit and made the ending a lot better. All he had to do was use the plot points and mechanics he himself introduced in og jjk.
Maru and Cross are twins. So them having a Maki/Mai style restriction woulda made so much sense. So their CT the asspull Harmony would be way weaker. Instead of them controlling the space ship with their CT, make it so that Dura(their mentor who died vs Dabura) left his CT and CE for them to use, and they used those to control the ship and escape their planet.
Have Cross actually die from the gun shots from the earth sorcerer. Give Maru and Cross a farewell scene like Mai and Maki. But instead of it being the "Destroy everything" that Mai asked Maki, Cross asks Maru to find a way to coexist with the earthlings so their people can survive.
After Cross dies, Harmony gets giga boosted and becomes what it is now. Maru's determination to eradicate curses so the simurians and earthlings can coexist in peace makes more sense with it being Cross's final wish too.
And Maru actually struggling against Tsurugi makes sense too since Harmony only became this strong like a few days ago. So he's still not fully capable of controlling it.
Make it so that one of Tsurugi or Yuka also actually die. So both sides lose someone. So they can actually see eye to eye.
These changes imo woulda made the ending better, even if slightly.