Where's all this bullsh*t coming from, that Naruto lost his powers?
Last time I check after sealing Kaguya,
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Naruto still was able to transform into Six paths Sage mode (六道仙人モード, Rikudō Sennin Mōdo) against Sasuke.
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The Manga only showed Naruto losing Hagoromo Sun-seal. Mind you even Sasuke lost his Moon-seal.
Now about the Movie, Naruto didn't use Six path Sage mode against Toneri simply because Kishi didn't wanted to Spoil the transformation to Anime viewers.
Logically, we can even say Naruto also didn't use Six path Sage mode against Toneri because Matured Naruto might be too OP using that mode against Toneri.
QED.