Honestly what would have been great if Green Bull more of a stealthy, careful type Admiral, sneaking his way into and around Wano, using his DF to hide and thus camouflage himself and gain surveillance/intel on whats going on.
Maybe have him even going underground and finding the potential corpses of Big Mom and Kaido or if not, maybe even finding Pluton first and thus the Marines get an Ancient Weapon and a massive, much needed gain and power boost.
Green Bull's nickname would then be ironic BUT I think he's meant to be the character, like some people when they play stealth games like me, either take the approach of "killing all the enemies means no witnesses regardless" or in this case, they do try to stealth as I do sometimes but when caught or cornered, they turn fierce so to speak and fight back brutally, like an enraged bull even.