Or maybe Oda hyped and setted up things that never happened or worked in ways that went against the story as a whole.
Just to subvert readers...which happens in many great failed pieces of writing.
He dragged the arc way beyond its intended endpoint which should have been the end of the Tea party. This is where having strong editors would have helped to cut down all the new ideas he suddenly began developing as the arc progressed. This was the arc where the editors were basically hyping another arc (Wano) while it was still ongoing. Shows how little they really cared for WCI.
By the end, nothing of note was really resolved. The status of FI. The Status of Germa and the Sun Pirates. Even Jinbei. And Pudding x Sanji? left all ambiguous and in the end reset to 0. And Sanji feeding his enemies as a call-back to Baratie? why? that shit was already done with back in the Baratie arc. No need to rehash it here just to make the same point (Sanji will feed anyone hungry)....
any wonder the arc ended the way it did. And never mind Oda having to do a chapter using Morgans to 'explain' that this was Luffy's win - it wasn't. Luffy and his half crew were chased out by a spoiled entitled child the arc ended with BM's win and Oda had to retcon it after the fact 'Fifth Emperor' indeed phah.
Guess a few of the Japanese respondents felt the same way.