Luffy's strength grew in Wano, reaching Yonko level with Gear 5 and Conqueror's Haki. Imu is a powerful enemy, stronger than anyone Luffy has faced, and even pales compared to Kaido.

Luffy cannot do something like this with his Haki, and there is clearly a need for him to grow stronger. Gear 5 on its own is not enough for him to reach the top.

But, if he's wielding his axes, then Luffy and Zoro need to be careful. One Piece chapter 1140 could show fans a glimpse of Scopper Gaban's Conqueror's Haki, provided he goes all out.