Meh, Sanji got his WCI arc and was not so bad even if there were points I don't liked (he kicks Luffy in the face but it is resolved immediately, I mean it was not bad how Oda handled and developed it but I hope for something like Enies lobby with Usopp or Robin) but in the end there was no real development (Sanji had no developments character wise, we know more about his shitty past and that is it), then he get the power ranger suit for a bit, the best point is that he get rid of it soon after even if now he has the exoskeleton power.. Oda could keep going on with the kick/legs power ups. Anyway he had his moments and even if pre skip he was better (dame can be said for every SH, especially Luffy) I think he is somewhat still Sanji.
Then Robin. She has 2 faults which are new / way bigger than her pre time skip self. First the ones who got way bigger are exactly the same as Nami. She is a walking fanservice, pre time skip at least she had a character and that is the 2ns mistake. She like every other secondary SH got sidelined and/or turned in something else (her and Nami are fanservice, Chopper is the mascotte, the other simply got sidelined). Just looking at Wano she had a brief fight with the spider lady, displayed a new power, couple of fanservice panels in the bath, she visits the poneglyph at the end of the arc but it seems Oda put her in that scene only because he had to do it. He didn't even gave her the honor to read the stuff on panel or make some comments. Just what he had to do (but we can use chapters and chapters if there are tontattas or old hags screaming weeding cake).
So imo Sanji. His character at least kept his shape while Robin is something else and is almost eclipsed to make space to all the secondary characters Oda has to introduce every arc.