I'm not sure I'm following you. Are you saying that incorporating actual real World human emotion, and having it play an integral part of a characters growth, tribulations, and inner turmoil, is less logical than the "I'll suck it up because I'm a tough guy" trope that riddles fictional characters, and in no way shape or form actually mirrors that of the real World? Is it different? Yes. Is it cringe to witness? Somewhat. But illogical? Not at all.
Sanji's mental/emotional struggle is simply another avenue towards greater strength compared to let's say the physical struggle Zoro has to go through in that same pursuit.
Oda has basically answered all the grievances people had when it comes to Sanji becoming a Top Tier.
He restricts himself in combat => body modifications to make up for it
He doesn't train to get stronger => upgradeable power suit and powers that use emotions as fuel instead of just the physical body
The "Just a cook" who restricts himself, doesn't train, and doesn't pursuit strength as his main goal, is basically turned into a super soldier with a power suit who's bound to get stronger, but has to come to terms with the nature of his ever growing powers, and how that does not have to define him.
And the beauty of it is that Sanji is having this mental/emotional struggle only because at the end of the day, he's nothing like his siblings, so that's the first thing he's going to have to acknowledge, but it's a difficult one without an outside perspective.