I just rewatched Yuyu Hakusho and it became obvious real quick nothing planned from arc to arc. Even when the creators want a clean end, their editor will push for more if it's popular enough. I can respect Demon Slayer for committing to the final villain that was setup in the beginning.
That's not the case with one piece though. The main long story is the highlight of the series, it just happens to be microdosed in between several "shorter" stories that don't work that well because they are usually just excuses for the author to come up with new levels of weird character designs.
In some level that's all that one piece is. An author wanting to draw weird characters and make tom & Jerry style jokes. Somehow at the same time there's another level where it is a deep story with plenty of social critics and political discussion.