Yeah but you know what happens if Pucci dies or be erased off the universe if Dialga is inside the universe (including Palkia and Arceus) the universe will reset and the entire world would be different especially the three pokemon.
Mhm, but what happens if instead of being a powerful Pokémon in the new universe he's actually a weak Pokémon? Therefore, Jotaro and Jolyne (now named Irene due to universe reset) will have a chance to win against it.