You have a strange definition of vital. I would say he’s been present in just about every single arc, I would never say he was vital. Only one person has been critical to their success ain all the arcs that they’ve participated in, and that’s Zoro.
Don’t give me wrong, there are some arcs where Sanji was actually vital to the straw hat success, but it’s definitely not all.
I mean, let’s face it. Not only did he try to abandon the crew, but the only reason why he beat queen is because queen was softened up first. Same reason why he’s gonna be able to beat Sommers later.
I’d say just about every arc in the New World, Sanji acts guaranteed the straw hats success in the New World .
Punk Hazard - Sanji was the one who connected the crew with Kinemon and saved his life’s which ultimately led to the entire Wano saga.
Dressrosa - Took down Doflamingos entire intelligence network, saved the Sunny, and stopped Doflamingo from taking back Momonosuke
Zou - Does it even need to be said? All of Zou call Sanji their hero and he stopped the BMP from kidnapping the other straw hats
WCI - Saved the lives of every single straw hat in the arc. Luffy on cacao island and the other straw hats by stalling big mom with his cooking skill.
Wano - Without him Momo would’ve died so Luffy wouldn’t have made it back to the rooftop and Kaido would’ve killed everyone.
Sanjis been easily the most vital straw hat of the new world. You’re just coping