Remember Whole Cake.
Sanji's arc. But a Cake.
If Oda want's to have Sanji fine for the end of Wano, he won't allow him to fight against someone like King or Queen... But Jack??? And a Nerfed Jack??? LMAO, perfect for him.
It's bad enough to be a good contrast for the end...
haha I know this seems bad currently but don't worry Sanji will shine
WCI was never meant to be an arc to highlight Sanji strength and powers and might.
WCI was Sanji winning over his inner demons and showing his true strength to the Vinsmoke : he has emotions, he cares, cares for the weaks, for his family, his crew etc. Sanji managed to free himself from his past and can now look in front of him instead of behind. He even saved the Vinz when they were 2 seconds away of being killed.
Sanji didn't lose anything when the drug didn't work for him, Sanji on the opposite was better than them.
Sanji proved he was superior to Judge puppet soldiers : he saved them, he put aside his past with them to save them, he stayed true to his character through and through. Sanji won against his family. They can trash talk him all they want, they are not his bruden anymore.
Sanji baked a cake to save all the islands, we can think it is a bad plot (yep it was weird as fuck) but this is not against him power wise.
Sanji arc was not a fighting arc it was a character arc.