Him getting CoC before Zoro wouldn't have felt right. And the idea that he needed to get it in WCI because it was "his" arc, is arbitrary. If that were true, we wouldn't have had that whole development in Wano with him getting the exoskeleton and destroying the RS, all of this would have happened in WCI. Not everything related to Sanji's character development has to happen in a single arc.
WCI is Sanjis most stressed arc where he is pushed to his limit, this should have been is CoC moment. Using Zoro as an excuse doesn’t work too well. (This arc even gave him a bounty higher than Zoro’s)
Wano closes that door on his confliction he even states Luffy doesn’t need him to be a someone who can crush someone like Queen with ease, Sanji just need to be Sanji a kind hearted person.
Plot will give him the boost he needs, just like Wano and Eneis Lobby.