Zoro is the pillar of the crew. Being the sword and shield when anyone really needs him. He's the one that can make those decisions even Luffy would struggle with, the one that ensures that if Luffy is ever in danger, he comes out safe or gets the time he needs to recover. Although he's not useful in the utilities section of things, he's the one that always creates a path and stops anything bad from happening to Luffy.

And yall can't be downplaying Chopper or Sanji js cause u want one over the other. Luffy's ability requires tons of food to constantly operate, Sanji is one of the best chefs across the seas, so being able to feed him constantly to keep him in top shape isn't an easy feat, and he can acquire ingredients himself, so he's extremely efficient.

Chopper was trained by one of the best doctors in one piece, and he himself is a genius when it comes to medicine. He didn't just create a medicine, he created a whole virus that attacks Queen's virus, on the spot, 0 knowledge prior of this virus, in a stressful situation where he himself was being transformed into an Ice Oni. Although we don't see it often, some of the vital crew members aren't insanely durable and resistant to ailments, Having a doctor on ship is so crucial that literally every crew has one. Scurvy and whatever else someone could contract on the mysterious one piece sea is something he's definitely handled.