Zoro using adv CoC despite having no control or awareness of base CoC was a major kick in the teeth and just proved Zoro needed a massive boost to get to YC1 level and how broken Kozaburo's masterpiece Enma truly is.
What are you talking about?
Zoro knew about CoC since the beginning of post TS. Zoro obtaining ACoC was better written than Luffy obtaining internal destruction haki. Luffy didn't even know that was a thing nor was he able to use flowing before. At least Zoro already knew about flowing and was very skilled at flowing his CoA haki. All he did was apply that flowing skills to another type of haki.
Rooftop Zoro was already on YC1. He was stronger than any of the other rooftop SN at the time. He needed ACoC to hurt King because King's durability/defense is that strong. Having the power to hurt and cause significant damage to a Yonko (Kaido) doesn't mean you have the power to hurt King. But of course you don't want to acknowledge that because that means current Law and Kid may not have enough power to hurt King.
Enma didn't give him anything. That has been proven time and time again. It was a burden and actually made it harder for him to control his haki.
The only problem is the number people who couldn't believe you need to be a conqueror to be the WSS. It makes perfect sense because the WSS is the king of swordsman.
When we look at all of the characters in the manga we still only have a very small percent of people with CoC/ACoC so it's still a rare power. Just because the manga focus on those characters with that power doesn't make it any less rare.