It's pretty surprising to me how many people read One Piece for the fights, when it's easily the weakest part of the story. And that's because it's not about the fights.
They are often just a vehicle to progress the plot, a battle of wills more than anything else. There's a reason why even characters who aren't combat oriented (like Usopp, Robin, Nami) end up in fights and get their asses kicked. Then suddenly they shout that they believe in their friends/Luffy will become the pirate king, and somehow come out on top by the end.
It's to show that they have a greater conviction in their dream, and a more righteous goal than their (typically) sleezebag opponent. It's not about who can punch harder or who put in more time training in the hyperbolic time chamber or conjured the perfect nen beast after maintaining Ryou for 16 hours.
Sanji is one of the few combat oriented Strawhats and - what a shocker - even he's just the ship's cook! After we just got an entire arc centered around Sanji's personal conflict and growth, it absolutely blows my mind that people are still expecting some sort of training arc to show how his Diable Jambe got 5 degrees hotter.
Maybe, follow me for a second, this arc isn't just about some war. It's also about the
burden of inherited will. Momo being forced to live up to his father's image, when he is a coward and a weakling - having to sacrifice decades of his life just to be useful. Yamato being the daughter of Kaido, wanting to be like Oden but simultaneously
not wanting to be the Shogun because that's what her father,
Oden's murderer, wants for her. No wonder she got along with Ace, a guy who was executed for being Roger's son -
executed for the crime of existing. And Luffy inherited that from him, having to shoulder the burden of an entire country simply because Ace could never return to fulfill his promise.
Robin, the Ohara demon, having to come to terms with her past and embrace the image of a demon that people place on her. Was this some asspull, too, just because we didn't watch her train Demonio with the Revs for 10 chapters?
And now Sanji. A guy who hates his family lineage, who doesn't want to be associated with Judge. But in order to save others he is forced to use his raid suit - his father's creation. At every possible turn people refer to him as Stealth Black, one of the Germa, son of Judge. It happened in this exact chapter, where he's even fighting a
former colleague of his father's. No matter how much he runs away from it, he benefits from being a Vinsmoke. And now he's truly becoming a monster like his siblings, all because of something completely out of his control.
The whole point of this is that you can't run away from who you are. You can't escape your fate. You have to embrace it and turn it into something positive, make it your own. It's not about some highly intricate kung fu powerup that Sanji spent 2 years learning with the Okama to master. It's about destiny. This was already laid out in plain English right at the beginning of the story, remember?