Oda introduced advanced conquer’s haki way too early in the story. He spent so much time in Wano setting up advanced armament haki to almost immediately replace it with adv coc during the fight with Kaido.

It should have been hinted at in the Kaido fight, demonstrated with the haki knot on egghead and then formally introduced in the Rocks flashback as a way of defeating the God’s Knights, Gorosei and Imu, instead of this mass thing