It's also that there's no fluent narrative. There's a feeling I get from Oda as a storyteller and it's that his events don't seem to flow, many of his subplots don't seem to develop organically until they converge into a climatic resolution but simply are concatenated like a series of scenes that need to happen one after the other. And this becomes even more annoying when the same event seems to repeat itself over and over, like Orochi being beheaded only to remain alive, Kanjuro returning from his defeat or Kaidou fighting people over and over.
It gets to a point you just don't care.
