There's nothing wrong with it, in and of itself.
It just happens FAR FAR too often.
Just give me a chapter of all 9 Straw Hats on the Thousand Merry, just having a damn good time, like the good ol' days.
Those "good ol' days" literally NEVER happened. You get like a chapter of that between arcs. The crew has literally ALWAYS split up during story arcs, even when the crew was only Luffy and Zoro (seriously, go back and look at how Orange Town starts).
The crew splits up for the fight against Kuro in Syrup Village.
The crew splits up at Baratie with half the group going to a completely different island.
The crew further splits up at Arlong Park.
The crew splits up upon arriving at Loguetown.
The crew splits up at Whiskey Peak, with only about half the team learning about Crocodile before they leave.
The crew splits up at Little Garden with half hanging with one giant and half with the other.
The crew splits up at Drum into 3 groups (Luffy-Sanji-Nami, Vivi-Usopp, Zoro-Carue).
The crew splits up several times at Arabasta.
The crew splits up at Jaya, first in Mock Town, then when Luffy bails to beat up Bellamy.
The crew splits up at Skypiea.
The crew is split up by the rules of the Davy Back Fight at Long Ring Long Land.
The crew splits in many, many ways at Water 7 and Enies Lobby.
The crew splits several times at Thriller Bark.
The crew splits up at Sabaody, regroups, and then gets semi-permanently blasted apart.
The crew is all split up into groups still on their return to Sabaody.
The crew split up immediately upon arriving at Fishman Island.
The crew split up at Punk Hazard.
The crew split into several teams at Dressrosa.
Spoiler Alert: the crew is going to split up when they reach Zou/whatever-the-hell-the-next-island-is.
