Zoro has yet to do something in wano that can impact the plot. Luffy about to beat Kaido, Sanji saved Momo (2nd biggest impact to the plot), about to beat Queen. Zoro about to beat King. Zoro scarring Kaido have 0 impact, Kaido is still healthy af, either way plot stays the same. All Zoro thinks is i'm gonna cut him, him and him. Whatever Zoro does, doesn't affect the plot. Bland as he can be, always at the side of Luffy or Sanji to be carried for plot. Oda bad writer when it comes to Zoro.
he doesn't need to affect the plot outside of fights that much
It's kind of the point, sometimes he affects the plot but obviously he won't affect the plot that much, so it's not surprising he doesn't affect the plot outside fights
Think about it this way
luffy is 50% a powerful fighter, 50% an impactful character
Sanji is 40% a powerful fighter, 60% an impactful character
Zoro is 60% a powerful fighter, 40% an impactful character
It's not that complicated, lol