Well whatever you say Shishio, but Shanks feat of using CoC against Ryokugyuu is the best CoC feat so far we've seen. Even is greatest like Roger or Xebec aren't alive anymore but we've seen things from other greats like WB, Rayleigh, Kaido or BM. Rayleigh or WB are someone who's quite old so we shouldn't be expecting much from them.
Next thing is Shanks ambition weren't small ever, he was freest man on the sea before which is similar to what MC connects with PK level. And now Shanks even aiming OP as well. So how his ambitions aren't big ? It is something Mihawk said that even difficult than surpassing himself.
There ain't any CoC feat or facts from others dialogues that someone's CoC could simply even able to affect a mid/high top tier. Though Shanks been showed using it on such scale for the first time in the series and that is even after the fall of Kaido, WSC, whose strength/feats were fully revealed than it's safe to assume that only 3 or 4 more people can achieve that level on CoC. Most probably they would be Roger, Rockss and Luffy. Other than these three only Dragon is left with such high level hype and mystery.
As for how CoC works amongst different power level, Oda has described it before too ,
@comrade @MonsterKaido @Bogard would like to know your opinions as well guys :
Also you take it in wrong way Shishi
Oda Said CoC only affects and helps in removing those who are worthless but that comparable to you powerlevel. Oda in that interview took 100k fodders as examples and compared it with both Ray and Shanks. Now for both Rayleigh and Shanks, all those present on the opposite side of Luffy at FMI are really worthless to get destroyed by there CoC by ease coz difference in strength is really huge. I hope you don't have any issue with these facts.
Now Shanks haki is something which is even hyped by those who were there with WB since his prime while also have seen legendary Roger and Rayleigh fighting as well, but still made a comment on his Haki level.
Shanks Haki or his strength level should easily be judged by this as well when just the throw of CoC from miles away paralyzed a top tier like Greenbull. The difference in strength is definitely significant here.
Won't be expecting much and might be wrong but from Oda's description on CoC and how Shanks affected Greenbull is clearly stating his strength. Even WSC's CoC wasn't this overwhelming.
As for the rest of the post, it's quite biased looking but would like to say, Buggy became an emperor coz both Mihawk and Crocodile are at his base while flyer interpreted like he's the boss. So it's not marines mistake to take him as emperor while also believing he could tame those two. Though if you go through the context than you can see Mihawk and Crocodile's deal might be to work together (equal footing) but if flyer weren't wrong or things go without it than Mihawk would be the emperor. While from Mihawk's look and the way he stated his intentions, he was previously prepared for the position as well. Lol
Lastly yeah Shanks ain't comparable to Rockss pirate in anyway. But each and everyone of them has made a significant name and higher bounty than average for themselves on their own and all of them had quite a lot of faith and respect for Shanks. This is something which only be achievable through solid strength.
While for Rockss pirate, even though all of them were monsters but the current feat of Shanks for the balance of crew amongst all previous gen or current emperors is matchless.
So whatever someone else believes but Shanks strength, position and ambition are solid amongst greatest in the series. While his CoC feat isn't overrated in any way but he deserves it considering his position and strength. Without any care, the way he challenges every group at MF is clear proof whether its Navy, schibukais or BBP.