Ugh. Whether you hate Sanji or love him. Push the damn agenda and bias aside for one damn minute and only judge by character personality and the panels in the story.
The fact of the matter is:
Before the S-Shark fight, Sanji was quick to anger, and quick to fight. He had no problems lashing out. After the S-Shark fight, he has not performed ONE offensive move or even used Diable Jambe which is his basic go-to move since he created it. THIS IS ABNORMAL.
Then we have the Stussy thing.
Whether Oda wants him in the fights or not or he's holding back. It's still abnormal for him to never even use his fire when defending, or any of the scenes we've gotten with him.