That "bad writing" is something that you should have been accustomed, it happened in many arcs prior.
However if you had acknowledged that Luffy is the main character and how Shonen manga works then this wouldn't have been an issue for you.
This is wrong, zoro always places himself at high regard, and best proof of that is his comment when luffy used CoC at FMI.
Of course he places himself in high regard but his admiration for Luffy FAR out weighs that.
Zoro literally BEGGED his enemy to train him for the sake of helping Luffy achieve his go. I dont think I even need to mention the thriller bark scene.
Zoro is the right hand man for a reason