I'd have to disagree. Sanji is the most fleshed out character personality wise out of all Strawhats. It makes perfect sense and i'll tell you something more, Oda doesn't follow the has-to-be-cool main character criteria in Shonen which makes One Piece in that regard even more unique to it's genre.
It's not about the "need to be cool" with Sanji anymore.
His character post-skip is a walking comedic relief and borderline sexual predator. Those are the main two themes - actually the only remaining themes with his character. There's nothing else to his character anymore.
FI: Do I really need to talk about it? Nosebleed running gag.
PH: Do I really need to talk about it? Body Swap + groping running gag.
Dressrosa: Was written out of the arc, after he was simping for Viola and then got no-diffed by Doflamingo as a hype tool.
Zou: LOL
WCI: Crying little bitch, that was ready to abandon his crew, violated his friend/boss , got embarassed, belittled and ridiculed by his family non-stop (not resolved at all) and then ... baked a cake.
Wano: Sexual predator that actually betrayed his own beliefs ("I'll never wear that raid suit!") and then only used it to stalk his defenseless, unknowing female friends, when they were naked in a bathhouse. Bonus points: Got utterly embarassed in front of whole Onigashima.
Compared to his portrayal pre-skip it's an utter disgrace.