The show dares to tell and incredibly long and ambitious story that defies genre standards.
Despite the modern anime market arguably being oversaturated with all kinds of different titles — that sometimes genuinely struggle in competing for the viewers' attention — the majority of them still prefer to do things 'by the book'.
Using standard character archetypes, coming up with generic settings and telling predictable stories. One Piece, on the other hand, was never afraid of doing things differently and its latest episode (1078) is another great example of how the show is not afraid of taking big risks with its storytelling.
Episode 1078 lays down a what's looking like the final puzzle of its seemingly never-ending Wano country arc — a thread that has been going for about 200 episodes at this point and with some of its conflicts and plotlines being set up back at the time of Punk Hazard arc, a whopping 500 episodes back.
To call this kind of approach towards storytelling 'risky' — would be an extreme understatement. The shonen genre in general is quite notorious for the unwillingness to diverge from its many tropes, including those dictating that a typical story arc of a fighting anime should be around 20-30 episodes, preferable even less.
Examples of shows' that manage to successfully break this rule are generally few and far between with a canonical one being Naruto with Chunin exams arc lasting for about 40 episodes and acting as a crucial point of not only the whole of its first season but the entire franchise's plotline.
Considering all of that, it is even more stunning that the one anime to break this rule and take a huge storytelling risk by setting up an incredibly long and ambitious storyline ended up being the most popular one that seemingly had no need to take such a big and dangerous gamble.
But then again, with a writer of Eiichiro Oda's caliber behind the franchise (the man sold half a billion comic books), it is not really surprising to see this kind of ambition.
And, guess what, with episode 1078's reception being overwhelmingly positive, it's pretty damn clear that this gamble was definitely a success. It would not be much of an exaggeration to say that Wano arc with its complex and all-encompassing storytelling might have set up a new high for the whole shonen genre. A high that is not likely to be surpassed by anyone in the foreseeable future.