Think that's a big problem with some parts of the community that see everything in the manga with the powerscaling lens, and think OP is in line with DBZ as a manga only about who is stronger.
Of course OP has a lot of fights, but characters go beyond that, even the one that are heavely fight-centered, look at Zoro, his biggest moment in the series wasnt he winning a fight or using some badass power, but he taking a heavy burden to protect his friends.
The Sanji fans, and some other like Ussop fans, keep this ideia that they want their characters to be stronger because they cant understand that stronger character=/=good character, and also they are unable to understand each SH place in the story in relation to Luffy, not that Sanji is weak, its clear that he is the third guy of the crew, but his character is more than just the fighting, Oda have done a lot plots with Sanji were he use his brain, expecially pre-TS, while Luffy and Zoro were clearly the crazy guys who love fighting, Sanji had this James Bond feel.
Probably a lot of Sanji fans feel really bad that Luffy and Zoro keep being cool characters post-TS while Sanji hasnt, he clearly suffered a downgrade in post-TS, and i'm not even talking about the WCI or he asking Robin for help, find those two great moments of development for his character, but i'm talking about he becoming the shit perv character.
Pre-TS Sanji was on of my favorite SHs, but since Fishman Island he have become the one i disliked the most.