I sometimes wonder how the people on this forum even have the brain power to simply breathe air. The average IQ here is less than 69. First off, Kaido used CoA very early on against Luffy. Second, King and Sanji used CoA in their clash. Third, do you actually think Queen and Jack don't have Haki? Haki is common in the New World. Shitters like Raisin and Bellamy have Haki. Within the Beast Pirates, Who's Who and Ulti, people who aren't even commanders, are confirmed Haki users. Every Scabbard has Haki. Revo Commanders have Haki. Yamato has Haki. Fourth, Kaido wants to have the strongest crew. Do you really think Haki training doesn't exist within the crew for those who have the potential?
Oda is just a bad writer in regards to Haki and I think he thinks Haki battles are boring. Rightfully so. CoO should have never existed btw.