I mean... they simply couldn't do it.
You are ignoring canon statements in the manga of characters placing Luffy's potential over Law's simply because Luffy used CoC ONCE accidentally in Marineford.
Just look at the reactions of all the Big Shots in Marineford when Luffy awakened it...
This is proper buildup about an ability.
You are severely underestimating that ability & the amount of hype, buildup & foreshadowing that went into it.
You are ignoring canon statements in the manga of characters placing Luffy's potential over Law's simply because Luffy used CoC ONCE accidentally in Marineford.
Just look at the reactions of all the Big Shots in Marineford when Luffy awakened it...
I'm simply implying that merely having CoC is not a reason to put that character ahead of someone who does not.
CoC is a strong ability and arguably the strongest, but to believe it makes the weakest users who wield such ability have more potential than those who don't it's false.