His overall story (what he seems to be leading to), has the grounds for good fiction and writing, but the separate arcs is where i feel he writes himself into a corner with characters and meandering plotlines.
For example, most people admit what they are excited for are the between arc updates, especially because those characters and plotlines are the most interesting.
I have argued that the series is heading back towards a peak again, because a lot of what we are seeing now is a result of the between arc updates. Kuma and Kizaru are big examples of this. Blackbeard, Akainu, Shanks, Mihawk, Dragon/Revos,Gorosei, Im, etc all are as well.
And these are the things and characters the story is leading to.