1) Lack of tension.I don't think anyone ever thought that the situation is dangerous after the prison mini arc.Ever since Kaido one-shot Luffy, which I admit was very cool and put their strength gap into perspective, it's either been all Ws or Ls that didn't cost ANYTHING.
Luffy was getting knocked out again and again but it was okay, he just came back after someone bought time for him and his defeats had no repercussions at all.
2) Big Mom should have been knocked out by Damned Punk.I don't get the bomb thing at all, it just makes the Supernova W look less impressive.Kid's attacks overall weren't nearly as impactful as Law's.
3) Usopp.He's literally a shell of his old self and it's been 10 years irl since he last did anything in the manga.From a very important character to the most neglected strawhat.That's really sad to see tbh.
4) Yamato.I just don't get the whole I'm Oden shit.Why couldn't they just be trans or something? Why assume someone else's identity? It's such a nonsensical decision.So many panels wasted on Yamato, that could have been used on Usopp/Chopper/Brook.
5) Retconned deaths (Izo and Ashura lmao), dropped plot lines left and right, Kaido literally having the worst backstory out of all one piece villains.
All in all, Oda started this Yonko saga back in punk hazard, around 400 chapters ago (~12 years) only for it to be rushed by either him or his editors or because of that dumb film red.Very disappointing arc, albeit still good.