The train was a whole mission Sanji went into, with the main goal being the Rescue of Robin. It took several chapters.
The bath scene was literaly a few panels and mainly used as a joke. And the off screened fight against P1 took also just a few pages. It's more of an side skirmish than anything.
In Wano there were tons of characters involved so ofc Oda could spare less pages for Sanji compared to EL. He didnt even had to spare panels for the sole Sanji after he just finished Wci but he did It regardless. His fight with Queen was also great and had plenty of character moments.
I dont think Sanji in Wano was done dirty by Oda, at all.
Reading it weekly has his pros and cons.
You for one notice and remember more details.
OP is the manga i remember the most details off, because i am following it week for week for a long time and i discuss it the most aswell. As for example Bleach, that i read about 1 or 2 years ago, i could read several chapters in one go, but because of that i don't remember all the details anymore, because i didn't give it too much thought or time to sink in.
But on the other hand, because you read it week for week, you spend more time discussing and analysing stuff, that leads to the fact, that you gonna notice plotholes and just bad writing in general, as someone who reads multiple chapters in a row - which can lead to it being less enjoyable.
I thing anime only watchers are someway similiar to people that are ''speed reading'' manga's. Even though they are watching it weekly they often forget stuff that happened very recently, because they are not really able to focus on the story writing because of so many things happening in a short time. So they don't get enough time to really process everything that is happening and often don't notice inconsistencies or bad writing.
I see it differently.
Only by reading a story "in one go" you can analize subconsciously its overall narrative consistency.
The fact that you can spend more times in analize a single chapter due to weekly reading its your own factor based on your passion. Most of people read the chapter and for the rest of the week are done with One Piece.
Its a very simple story, as much as you can brainstorm into it, you dont need to analyze it deeply to realize that some details like the past presence of Ace in Wano, Yamato's saviour looking exactly like Zoro, Yamato's existence, "Ryuma was a one eyed samurai", the Grim Reaper appearing, Zounisha arrival, Marco sending a misterious letter (i feel like we can go on forever) are totally pointless waste of pages, mostly fan service moments with the purpose to tease the reader into wanting to know further and read the next upcoming chapters of the story that did not lead to anything.
Reading it weekly makes the casual reader forget all the details he encountered and that will never be touched again, and will feel like he is reading something coherent. Will feel amazed week by week by these fan service moments that lead to nothing. When he will read it back he will simply appreciate the fact that he can now read the arc in its integrity without caring too much in details he already encountered, and will scream THANK YOU GODA.
This at least is my theory to explain why so many people are praising this total mess and asswriting fiesta that these latest arc have been...
I've had a similiar experience myself.
Only by rereading Wci (while flawed, a much more consistent arc than Wano) in its integrity after reading it weekly I realized that the turning point of the arc its fucking Pudding for absolutely no reason in hell confessing to an imprisoned Reiju the plan of big mom of betraying the vinsmoke family at the wedding and also with the occasion confess that she doesn't love sanji and that she made a fool of him. All of this ofc while Sanji is convinently listening at the window.
This is not a plothole, or anything, but how is it possible that this Mickey Mouse level gimmick is the best Oda and his editors could come up with to turn the events of an entire arc?
Pretty disappointing, but by reading it weekly I didnt realize of stupid and shallow the turning tide event of the arc is.
Without having at hand the great scheme of the arc in its integrity I did not realize of how really crucial that moment was, in constrast to how stupidly it was designed by its author.