I think the author really pulled some nonsense out his behind to make Sasuke lose the final fight. He barley had any power against Kaguya and barely used the rinnegan against Madara. He didn't even use Preta Path the one that sucks up all ninjutsu. We know Naruto is a chakra monster so that would have made Sasuke win the fight. Where was all of Sasukes rinnegan abilities like asura path and the one that pulls out souls? It should have been an easy fight for Sasuke especially when he had all bijuu, he couldve made them fight alongside him with his genjutsu. Sasuke even has fire and it beats Naruto strongest wind move. I guess main character cheat codes trumps all.