This.
Also, wouldn't that just be a testament to how strong Naruto has gotten? He did receive chakra from the Sage, and inherited his senjutsu, which has been shown to boost other attacks. His avatar is seemingly chakra based despite being Kurama's Bijuu form. He also has chakra of all the Bijuus (though I doubt he's using it now). Naruto's avatar is most likely much stronger than before, just as Sasuke's Susano'o has been getting stronger. I think Naruto is the only jinchuuriki that could keep up with Sasuke's Susano'o at this point. Bijuus are always weaker without a host anyway, any Bijuu would get one-shotted with genjutsu anyway. You're pretty much underestimating Naruto here.