They have this image of One Piece built in their minds which cannot be far enough from the current state of the manga.
They imagine that once she joins she will get a 1v1 fight in all the following arcs, fun interactions with the rest of the crew, and character development akin to Nami, Usopp, Chopper, and Robin's personality growth (which happened pre-timeskip for the most part).
That is why theory-crafting is very popular among One Piece fans nowadays, it is because they mainly read the manga to come up with headcanons they enjoy, but they do not really enjoy the manga itself.>>223773926
Also, whenever we are served a bad chapter (literally every week) they act like Wano and the New World by in large is still in the build up phase and that the satisfying pay off is coming soon.
Nami, Usopp, Chopper, and Brook have been incredibly underwhelming this arc, and all the scabbards have achieved nothing so far, but they still firmly believe we are just in the build up stage and that all of these characters will get their time to be useful later.>>223774342
They will never do.
One Piece has essentially become the Star Wars or Harry Potter of anime, it will always have people willing to consume its shitiest material and pretend they like it.