1. The Pacing: There isn't a single arc that isn't outrageously long. From drawn-out fights to lengthy (and usually dumb) filler scenes, I'd say about 70% of each arc is a waste of time and doesn't need to be there. The longest arc (Wano) is close to 200 episodes, and yes, they spend the entire arc fighting the same guy.
2. Length: It's not just that the show is drawn out, it would still be unbelievably long even if it the arcs weren't stretched to their limit. The anime has been running for over 25 years and the manga will soon reach it's 30th anniversary in 2027.
3. It doesn't have a clear demographic: Sometimes One Piece boasts idiotically cringe-worthy humor that only a child would find funny, but with dark moments, outrageous oversexualization of female characters, and blood, it's clearly not for young kids. But the series is so childish overall that it cannot be considered a show meant for teens.
4. Irritating Characters: All of the characters are either dumb or loud. I don't think there's a single episode that doesn't contain idiotic yelling. Luffy is so stupid and clueless that it's impossible to like him.
Would I recommend this? No. Never.
