Why would some people say that gatsby isnt the protagonist in the great gatsby?

Narrator Nick Carraway is talking about Gatsby. Nick is the hero of the exchange with the East, is the dream and fantasy of America's success. Gatsby can be considered the hero of the story of Nick. So some people say that the narrator is the protagonist.

But no! Narrator does not mean protagonist. Gatsby is the protagonist of his own fight to achieve the American dream; he personalizes with Daisy. The tragic end to this dream leads to the disillusionment of Nick and finally connects the two stories.