I'd argue One Piece being the same has actually been the biggest problem when pedal hits the metal.
For example:
Luffy's victory is the final victory of the arc.
When both present, Zoro and Sanji will be the final fights, with Sanji typically having his fight before Zoro.
The Monster trio of the past are the monster trio of the present.
Luffy will "lose" and then win, but mostly lose for however long the fight needs to get stretched.
Luffy will always have "down periods" with his powers, to facilitate the above, whether its G3's shrinkage, or G4's Haki cooldown, of G5's general cooldown.
Generally, Nami and Robin won't be brutalized by men in heavy melee the way the needle lady did Nami in Alabasta, and you usually have to hope they are fighting women if you want to see a good smackdown.
Due to Oda's trauma with an editor, he draws pretty women in a very stringent way (sourced from interview.)
Significant portions of an arc will involve running or approaching the enemy when you're Luffy, and Oda uses travel time to keep characters apart.
Metawise, fans always love comparing the New World arcs to the Paradise analogues.
Regarding "differences"
We could say One Piece became different when Oda made the choice to introduce the warlords, as he admitted. The story has massively expanded because of those characters, pulling it away from the version that only had the Four Emperors.
Because of the success of Marineford, Oda has been continuously testing large-scale battles starting in Dressrosa, and then following into Wano. We've also gotten more unique scenarios in between.
Because of the ever-expanding cast of characters, there are more characters required to service than in Paradise. This has led to real problems and we've seen Oda try to solve it, experimenting with the crew split. Right now, it manifests as characters just standing and watching. Still an ongoing challenge.
Because of his desire to beat Marineford, he's focused on getting as many pieces on the board to have as many characters have moments in final war.
Because of One Piece's length, Oda has employed developmental rushing tactics like slamming together fire island and ice island into punk hazard, and slamming together Dressrosa and Greenbit, therein giving us a follow up to the Nolan stuff and so on. (Sourced from interviews)
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I think on an existential level, if One Piece stayed the same, one could admire the dedication to some former identity, while others might question how that is even possible over 30 extraordinarily turbulent years.
If One Piece changed, some would say it's not what it used to be and might want that, while others would say its natural for something to change as the environment to change.
Practically, at the 30 year mark of continuous release, where you've witnessed the rise of the internet and the sudden exposure to the international market, its impossible to not change.
I sincerely do not believe that anyone here has not changed in some ways. Now imagine the sort of change that a man will go through, meeting his wife who cosplayed his character and experiencing horniness so great he enlarged chest sizes, then his daughters going from infants to college, all while he was still killing himself with alcohol and cigs, and 3 hours of sleep at night, while spending at least 14 hours a week speaking to editors, not counting hours speaking to voice actors and managing the franchise.
There's just some realities that have to be appreciated.
