This is a very valid perspective, but if you are only looking at the end product, what is HxH, what is Berserk?
Two uncomplete stories, the first where the arc of protagonist ended yet restarted and all the secondary plot lines are unfinished, Berserk not even has its main story close to be explained, countless of plotlines dropped. Do you hold the same standard that you have for One Piece for real?
HxH and Berserk are both series with better writing than OP in the majority (!) of their arcs.
A lot of that might have to do with the breaks those authors take, but analyzing the arcs in itself they are just more round (start - finish), thought through, better paced and include way less plot-conveniences/PIS moments (although one could argue that Oda just doesn't care much about the last point).
You also have to get away from the "but where is the plot going" question. One Piece has one major goal we are working towards (becoming PK and liberating the world) since the beginning.
Berserk and HxH don't work in that classic way. You have multiple characters with different problems and each arc has its own goals that oftentimes just form themselves at the start and then even change due to circumstances changing. In HxH Killua at one point even talks about this, that his goal is to find a goal/purpose he can work towards. Both Berserk and HxH are way more episodic by design/choice.
That doesn't mean that Oda doesn't have his own great arcs btw. Interestingly enough he always shines, when he has some kind of lore/buildup arc and doesn't try to write his usual "fight arc".
Jaya, Water 7 or Sabaody can compete with any shonen arc in terms of writing.
The problem are Oda's longer arcs like Alabasta, Fishman Island, Dressrosa, WCI and now Wano. They usually start nicely, but around the middle of the arc it seems like Oda always reaches the point where his pre-planned story stops and he has to freelance a lot. Then the second halfs of those arcs really drag and have questionable decisions and conclusions.