No, he didn't understand.
Even though Sanji has the power of his hated father, his fight triumph will still be his emotions.
Emotions were the thing Judge hated most about Sanji, so Sanji having the Judge's power used for good using his relentless emotions to triumph over an evil tech genius will be an excellent answer for the average reader.
Dude, it's the rejection of everything that reminds him of a traumatic past.
He doesn't reject the powers because he doesn't feel like they are useful.
He doesn't reject the RS because he doesn't like the cool stuff it can do.
He rejects these things because they remind me of a point of his life of basically nothing but misery.
Which is different, for example, than the "not hitting woman thing".
The raid suit and genes are something he must swallow his pride and accept in order to become strong and protect his friends. He must accept the bad past, and realize that it doesn't define him now.
On the contrast we have the "Zeff oath". Which is something that reminds Sanji of a time of acceptance and love, from someone he deeply cares about and views as a father figure.
It's a matter of positive reinforcement x negative one. The negative reinforcement is much more likely to be surpassed by him, in exchange of a positive feeling of helping his friends. Which is why is kinda inevitable to him to make amends with his past.