Naruto fell off a cliff after Yahagi left.
He was Kishimoto’s editor and mentor for the first 402 chapters and had a major hand in shaping the story.
He left right after Sasuke VS Itachi, and just before Naruto VS Pain.
The manga went on for another 300 chapters without him and got worse and worse in every regard. Even the thing that got Kishimoto to the big leagues - his cinematic style - took a hit without an editor of Yahagi’s calibre to work with.
Yahagi era Naruto is still good, but everything after has aged badly and will continue to.