I think it's a failing of Shonen production and editing. In order for the power creep to get across to the readers, successive battles must be bigger and last longer.
It'd be no good if the protagonist defeated the last boss in half the time it took to defeat a mid-boss! So, as stories get on, battles become longer and longer, for no real reason other than they must be longer than the previous fight.
It's conventions like this that are usually seen as the correct thing to do by editors, but it's when a story successfully breaks these conventions thta it becomes a breath of fresh air.
Of course, bigger companies dont want to take risks. Only smaller publishing houses can do that!