You are really not getting this. I’ve already said it.
I did not say what Sanji did when he gave up in WCI was not, by real world standards, rational and logical.
I am saying that in the OP world, Oda has made it very clear that it is considered to be more impressive to choose the seemingly irrational path and put all your faith in yourself. That is the sign of people with the greatest willpower, and the greater the willpower, the stronger you are.
This is a series where Oda portrays it as a good thing to fight against seemingly unbeatable odds. Zoro fighting Mihawk, where he was certain to die, is portrayed as the unambiguous right thing to do. Zoro continuing to fight against Mihawk knowing that he was completely outmatched and about to die, unambiguous right thing to do.
What Sanji did on WCI was never portrayed as the right thing to do. It literally accomplished nothing and saved no one. Big Mom had lied to him and was going to kill the Strawhats anyway. Sanji and his family would have died anyway.
Sanji was unarguably totally in the wrong for not trusting Luffy and giving up, and he had to accept that later in the arc.
In the meantime, the admirable figure is Luffy, who refuses to give up on Sanji, and against all the odds tries to fight Big Mom’s army, tries to rip off his own arm to escape prison to save Sanji, and says if he needs to he’ll go back to East Blue and fight to protect Baratie.
That’s why Luffy’s haki is much stronger than Sanji’s. He’ll do the seemingly impossible route and try and fight, but that gets rewarded in the end. Giving up is not rewarded. It ended up with Sanji crying outside Pudding’s bedroom and planning