User blog comment:Keekian/Will OP be better if Luffy was smarter?/@comment-1784001-20170417160024/@comment-24850639-20170418150354

I see what you're getting at, but that scene was moreso about emphasizing Sanji's importance to the crew. Eating in general is something that is an afterthought in most series, but with Oda making such blatant connections to energy and rejuvenation (and fighting techniques in Sanji's case), missing someone like Sanji became absolutely crucial. Look closer at the fact that someone tried to be in Sanji's stead and it failed miserably, than Luffy being his usual idiotic self. As insignifcant as being a cook may appear on paper, it actually carries a great deal of responsibilty to the lives of your crew, and that scene/this arc showed that only Sanji can truly fill that role for the crew. Luffy needs Sanji's cooking expertise just as much as he needs his strength in order to become Pirate King.

On another note, you can also look at it as a plot device for Whole Cake Island. They were going to an island made completely of food, it wasn't necessarily like Luffy was dooming his people to starve.