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.
I'm glad the arc didn't end after the tea party because escaping from a Yonko's territory that easily would have been stupid imo. Showing the escape along with the sacrifices and those staying behind to help the SHs escape was to show how dangerous a Yonko's territory is, and that simply escaping would not be that easy. However the whole escape did drag out for way too long and it could have been shortened, imo instead of having Big Mom go on her hunger rampage and chase after the SHs she could have just stayed behind at WCI and ordered her crew to go after them. I think most people would have been fine with that but the problem is that Oda already setup Big Mom having hunger rampages since the beginning of the arc, and we knew at some point in the story that was going to end up playing a role again.
The other reason why Oda did that whole hunger rampage for Big Mom was to have Sanji be the one to make the cake for her, while I know some people didn't like it Oda was going to have Sanji play a role with his cooking in the arc no matter what. WCI was an arc focused on Sanji's character and he's a cook first and fighter second, so of course Oda was going to plan something major for Sanji that involved cooking. I still wish Sanji at least got one major fight during the arc but I guess Oda wanted to save that for the Wano arc, but yeah when it comes to the escape some stuff could have been cut so that way the arc wouldn't have dragged out. The escape imo could have been 10 or 15 chapters instead of it being over 30.
If Oda did that then WCI arc would have been at least around 60 chapters instead of 78, pacing was definitely the biggest issue during the second half the arc along with Big Mom screaming wedding cake all the time. Personally I still liked the WCI arc despite the problems with the second half, also the arc for me feels a bit more better when binge reading it compared to reading it weekly and imo the arc was done a bit more better in the anime.
Also based of that popularity poll in Japan it seems like the Japanese readers like arcs that either have war/battle royal or have a Japanese theme to it. Zou and Reverie two arcs I know that many love, and some would even have one of those two as their favorite post timeskip arcs are not even on the Japanese popularity poll. Arcs like WCI, Zou, Skypiea, and others not being on the list doesn't mean those arcs are bad its just that the Japanese readers have their own personal preferences when it comes to which arcs they like the most. For anyone that tries to use that popularity poll as an argument to prove that an arc not being listed there is a bad arc don't because it's ridiculous and pathetic, using a popularity poll to try to prove something is just dumb and also we only saw the top 5 favorite arcs not top 10 or even top 15. Everyone in the world has their own personal favorite arcs, while it is cool to see which arcs the Japanese readers like the most, it isn't something to make a big deal out of it.