It seems a bit silly to expect that the end of One Piece won't have some kind of hithertofore unprecidented escalation of all the crazy rivalries, wacky powers, and different factions in the form of one final brawl.
Perhaps that isn't your cup of tea! But I think the fights are difficult to extract from the narrative when you're talking about the climax of the entire series.
I'm personally not overly fond of the Marineford arc. But that came from a lack of emotional investment in many of the characters.
If it's the Strawhats, on the cusp of achieving their dreams, it will be quite a different story, I'm sure.
At the very least, I have faith that Oda knows what he's doing with the ending, considering he's had it in mind since beginning the manga, and drawing the final chapters has been part of his motivation for continuing serialization for at least as long. Whether it comes in the form of the greatest discovery, the greatest battle, the greatest party or the greatest conversation, I'm sure the ending of One Piece will be... well, great.
And frankly, it's a bit premature to speculate negatively about a plot development that won't happen for at least 5 or 6 years.