Oda's obsession's with Luffy being the most popular, holds One Piece back.
Where it would make sense for Zoro to step in, Oda can't allow it. Same thing happened with Law too, he nearly beat Luffy in votes during Dressrosa after Punk Hazard, he was always going to be put in his place. Oda will contort the plot all sorts of way to make sure Luffy is worshipped, no one can look like they're on his level even if they are.
Calling Luffy the 2nd coming of Ryuma was shameless.