When Oda created Sanji he didn't think about how to develop his dream, it's not like Sanji jumps into the sea and swims until he finds All Blue. With each fight of Zoro he is directly closer to his dream getting stronger and stronger, but Oda has no way of developing this direct build towards Sanji's dream. This doesn't just happen to him, it happens to Nami, Franky and etc.
So all these characters ended up turning into honorary fighters. Their most important activities are as fighters and not with their respective roles.
Let's take the example of Sanji which is the topic. His main function should be to feed his teammates, but SH separates and his function is not necessary. In Dressrosa, their captain eats the local food, so when the WCI happens, others of his teammates go to Wano and Sanji's food doesn't need it either, Zoro manages to keep eating sick lizards, the others eat something in the capital and etc.
So Sanji, who was the cook, is now a fighter, his main contribution to the crew is the fight, we've already seen that if he doesn't cook the crew can keep going, but if he doesn't fight the crew has an embezzlement.
And here we come to their answer, they want Sanji to be like Zoro because Zoro is the one who contributes the most to the crew as a fighter, so Sanji is erased. As his function, which should be the main one, is poorly treated, it's only left for him to fight, but Zoro takes the focus away.
Zoro was one of only two people who managed to tag Kaido and did so without Coc, which makes him even grander, but for the Sanji fan who can only cling to the expectation of him excelling as a fighter it's almost an offense, Sanji is portrayed as the closest to achieving Zoro's power in the crew, but even then he's far away and it bothers them because he's already been abandoned in his lead role.