That's like acknowledging only the main part of the story. The primary theme was Sanji's emotions and there was also the underlying one that he was powerless due to him having no exoskeleton. That, he was a normal human, powerless and with emotions. Reiju still had her emotions too and they didn't treat her as a failure because the exoskeleton was successful. So power is an important concept for the vinsmokes. It would be the best victory for Sanji and the greatest shame for them to show how emotions surpassed Judge's greatest technological achievement(his brothers) in power with his own abilities.
There are no flaws that Sanji can't surmount himself, after all he's a major protagonist.
Reiju wasn't like Sanji, didn't bear the burden of being the defect that ultimately killed Sora. Straight up told him that she wouldn't openly help them so that she wouldn't be ostracized like he was brave enough to be. The fact that he wouldn't hide his nature even without an exoskeleton to spare him most of the pain is what Oda showed us with Sanji, if we're talking about the primary theme.
He's a chivalrous and ultimately a very sweet guy at the cost of his own suffering, right?
Not a one of his blood relatives are tough enough to live and die by the innate code cultivated by Zeff. That's his victory over them.
Will he be stronger than them? Sooner or later if not now, because he's a main character and that's how it works. But that doesn't mean he isn't flawed as a fighter. Those flaws are also part of his code, intentional parts of his story that put him at a disadvantage. It's a point Oda brings up regularly.
The impressive thing about Sanji is that he shouldn't be nearly as tough as he is given the shit side of the family genetics and his relative lack of dedication to fighting. The RS evens the playing field where he hardly ever bothers to surpass others on his own