But
@ImmaIvanoM isn't wrong about characterization being a weak point in Loda's writing. Sanji's second backstory in WCI doesn't add much to Sanji as a character that his flashbacks with Zeff doesn't already accomplishes as nothing fundamentally changes about Sanji, and in fact constantly lies about Sanji being the "kindest person ever", which can't be further from the truth. Simply layering details on a character doesn't equate to adding complexity to them.
And speaking of Sanji's character, what has he done to accomplish his dream to find the All Blue? What has he done to alleviate his weakness to not fight women so he doesn't unnecessarily put his crew in harm's way? Have Sanji's 99 recipes play any meaningful role throughout the New World? Etc etc.
1. WCI
WCI expands a lot of stuff. For example, in Baratie fb we know Sanji is stranded & not with his family, WCI gives us the reason, he escaped from his family. In Baratie we didn't know why Sanji loves to cook, WCI gave us a reason. Even we know where the new limits of his feeding, he even let a mouse to eat.
2. Constantly lies
That's what you believe. Brook/Luffy/Reiju/Mom only said that Sanji is very kind, you equating that to the best saint is on you, not Oda.
Oda shows his kindness, in WCI context, by making Sanji rescue his family who traumatize & make his childhood a living hell.
3. Dreams
Other SH also aren't shown to pursue their dreams. Also Sanji's dream is finding a place in case you forgot, as long as the SH travels, he is automatically progress his dream.
4. Weakness to woman
This is a spoiler for Onigashima arc, don't read if you haven't come this far.
Sanji's subplot in Wano is that he finally willing to ask for help to fight women (previously in Enies Lobby he didn't ask anyone's help).
Another subplot in Wano is that he willingly put women in danger (putting Robin against a strong enemy), not just him babysitting them.
5. Recipes
He used it on Punk Hazard.
6. Layers
Adding layers is indeed giving depth & complexity to Sanji's character, because it's not just one or two things, but a lot of things.
Let's take bounty (iconic elements for One Piece) for example. Oda explored:
1. His non-existent bounty (when Zoro gets one) as the first part of Sanji's bounty subplot.
2. His bounty picture as the second part of this subplot (it's wrong picture, and then tied to Duval)
3. Later it's about his bounty name (it's a new name, tied to Germa/family)
4. After that it's about his bounty status (only alive, this is an unique status, tied to WCI plotline).
5. And most recently it's the number (tied to a pun about him).
You see where I'm going?
- For OP character writing standard, only Sanji got this much for his bounty.
- For animanga character writing standard, there is no mangaka who puts a lot of stuff to 1 element of a character.
Like, you don't even see Kishi expanding Naruto's story in each ninja ranks (something iconic there).