He can draw. I think his issue is that he isnt a risk taker. He does (IMO) lazy shots and composition and doesn't seem to go beyond what's expected/needed.
He does the bare minimum, which is fine, but for a sequel for Naruto, there are expectations that hes just not reaching. His art (at least as it is now) is fine, but there's no fluidity in his art; the characters feel and look stiff most of the time, and he doesn't like to showcase drama in action for effect (Like you'd expect Naruto and Sasuke vs Jigen and Isshiki to have wayy more structural damage), which in my opinion ties into his "good enough" style (Although most will say it's not good enough; I for one don't really care).
That's just my theory on it though. It just feels like if you wrote a very basic and bare minimum paper that gets you a C, and it's either, you're too anxious about your writing so the writing feels very clunky, and/or you're very comfortable with a C because at least it's a passing grade.