Tbh i think all of the strawhats could be pretty good main protagonists of their own stories
Yep, true.
Zoro can make a quick class about bushido rules or the history of swords, which metal is good for making sword and which is bad.
Nami can make a quick geography class, how to drain world map, the scale ratio, which color is used for mountain area, lake and sea, etc. Which kind of paper is suitable for drawing and which paper is bad.
Sanji can make culinary class about dishes and their nutrition.
Usopp can tell history of giant and which plant can be used for war.
Chopper with medicinal class, herb, how to make first aid medicine, how to treat sick person, burned person, frozen person etc.
Robin can do history class, or telling the books she has been reading.
Brook can do musical class, musical notation, how to unlock sense of rhythym etc.
But nope
We instead have dumbass Luffy as the MC who can only spam "want to be Pirate King" bullshit or acting like a chimpanzee 24/7.