Oda is so good at short punchy focused arcs
It's his biggest strength by far.
Oda is a great storyteller (mind you: storyteller is not equal to storywriter) and knows how to catch his readers with interesting themes/storylines.
His biggest weakness is simply setting up and executing the finale of longer arcs.
A lot of that has to do with him not being great at writing battle scenes and fights.
Another reason is that he always uses some kind of major threat to drag out the finale (bomb in Alabasta, Maxim + Advent of Thunder in Skypiea, Shinokuni in PH, Birdcage in Dressrosa and of course ... the Wedding Cake fiasco at WCI).
That's why he's so good in those shorter arcs. He simply isn't tempted to goof around with unnecessary stuff and drag out the arc. He focuses on the main plot points, which is much more enjoyable for the reader.