1. Pacing Issues: Obvious objective flaw. Having slow pacing, extensive flashbacks, boring fillers and drawn-out fights don't put it in a good spot. Do you remember overhyped and terribly prolonged Gear 5 fight? It should've lasted 1-2 eps at best, not 5 eps. C'mon. Enough of this milking shit!
2. Art Style Evolution: Art style has evolved over the years. You could say it's inconsistent. I feel that the earlier art from Wano was the peak which op could've achieved. You may disagree, but considering simplistic manga's art style it won't be any better. Even in Wit's remake it's doubtful we'll get anything better than Wano's art.
3. Female Character Designs: Some fans have criticized the portrayal of female characters in terms of their designs. Some argue that certain female characters are overly sexualized or have unrealistic proportions. I guess I don't need to mention 12 yo Bonny, right? It's not only females by the way. Basically most of characters are unrealistic freaks. I mean, kid may like it, but an adult 20+ yo, really?
4. Proliferation of Characters: With a massive cast of characters, it can be challenging to give each one sufficient development or screen time. Some characters are sidelined, leading to a feeling of neglect among fans of those particular characters, which is unforgivable considering how many eps one piece has. Many shows do better within much less number of eps and yet one piece fails to do so properly within hundreds, HUNDREDS of eps.
5. Predictable Plot Elements: Some argue that certain plot elements, such as the recurring theme of friendship overcoming obstacles, can be predictable. Also do you know what ending will be like? "The treasure was your crew you've gathered during your adventure, Luffy!" Everyone is happy, the end. Is there any reason to continue this farce? I mean, besides money from blind fans.
6. Long-Running Nature: The length of the series itself can be seen as a flaw by some. The commitment required to catch up or stay current with the manga or anime can be daunting for new viewers. Let's hope remake will rush through chapters. 3-5 chapters per ep would be nice. But there is one more thing related to this long-running time - maturity. Imagine this. You were watching op in 1999 as 10 yo. Now it's 2024 and it still airs. Anyone with healthy-senses would have dropped this by now. Luffy as MC is childish and immature even after 20 years (sic!). You say goofiness, I say terrible character writing. Being more mature is boring as Oda said. Possibly, but don't expect mature people to watch it, seriously. Seems like Oda wants to target his show to constantly childish adults and kids.
7. World-building: Is it really that good? Maybe to some. I consider it lazy and good in a way of milking. How made up on the fly infinite number of islands can be considered good? The crew finish their task on one island, they sail to another and so on and so on without the end. Endless adventure with no goal. No goal? Let's move to another flaw.
8. Endless story without goal: Point somewhat related to 7th and 5th. What's the point of the story? Is the crew's task to visit every island in the world and become more famous? So ridiculously high bounties at this point don't make sense. With such big bounties the whole world should gather to kill main characters. That money would be enough to live the way you want till you die. One piece was the known goal from 1st ep, right? But after dozens of eps I'm not so sure anymore. What I'm sure is that one piece was just a trigger leading to milked story. I bet with much worse recognition Oda would have ended it by now. Is it any treasure at this moment, non-material at least? Or is it just supposedly thing to keep the crew together till the rest of their days until they show up in every place of that endless goddamn world?
It's really tiring for anyone who's not blind and decides to continue marching through this streched-out story.
