Success and quality aren't the same thing, just look at most of the most watched movies such as James Cameron's Avatar movies, the MCU or the Fast and Furious saga.
One Piece has been a good manga for most of its history, until these last three/four arcs where the story clearly declined in quality with the manga flaws catching up with it, but it was never Shakespeare level of writing.
One Piece has been a good manga for most of its history, until these last three/four arcs where the story clearly declined in quality with the manga flaws catching up with it, but it was never Shakespeare level of writing.
