He's the author of the story that's more then enough pedestal, he ain't need no more. Didn't say he was the sole person, he has a team. But it's his name written next to author, writer and illustrator and no one elses. It's simple if it ain't written by Kishimoto in Manga, (or he hasn't approved it otherwise) it's filler.And what pedestal do you put Kishi the author on? I understand if you haven't got time for the Death of the Author essay but Kishimoto has never been the sole creator of Naruto from it's birth thanks to huge contributions from editors, SJ, prior influences to it's reception with animated adaptations and fan influence.
All fiction is in some form, plagiarism. Kishi doesn't care about his 'lore' or 'canon' over an audience's enjoyment of his series. Masashi Kishimoto also plays an active part in this expanded Naruto media and only wants his audience to enjoy the Naruto story. 'Filler' as a bad concept is a toxic fandom invention. So the only interpretation that matters is the audience.
I'm not even a fan of the anime/manga but really object to people being elitist to others when it's themselves they're fooling. Over something that's meant to be fun like stories.
Stick to Naruto ain't no one talking about other fictional stories.