Don't know if you're aware of this or not but the more you get to know about a character the lesser will be the hype surrounding that character. Every character gets over hyped at the beginning then his/her hype will get lesser as time passes. It's same for every villain introduced so far and Kaido isn't an exception. Besides don't you think what you're currently doing with Kaido is what the other people did with Shanks? Just knowing a bit made you put Kaido above the rest and you're calling people idiots for doing the same in case of Shanks.
No one is reading manga so badly that they actually think that if a character has more panel time then it means that the said character is stronger than others. Shanks barely had any panel time compared to other yonko.
I wonder if you're being serious or not. He did far more than just getting a scare from BB and losing an arm to a beast. And I am pretty sure everyone in this forum is aware of his accomplishments. Shanks received his scare prior to the formation of his crew which happened like 20y ago which means that Shanks was less than 20Y old back then. Just a glare of him was enough to scare the shit out the of the same monster which was responsible for the loss of his limb so anyone with basic comprehension should be able to deduce the fact that he lost his arm because the situation demands it not because he was weak enough to lose against a fodder sea king.
About his portrayal: We all know that BB was out of his mind at MF, he actually thought that he's the strongest and went as far as challenging both Garp and Sengoku at the same time. Same dude became so cool and openly admitted that he's incapable of going against Shanks which puts him above BB. So until we get something that proves otherwise Shanks remains superior to BB.
Much of same can be said about Akainu, he went as far as challenging all Wb commanders just to make sure that Luffy dies. Same guy was desperately hopeless to make a move when Shanks stood in his way. No matter how much people try to spin the situation by using excuses such as fighting another yonko is meaningless and all . It doesn't change a thing.
Shanks is one of 3 people with right capabilities to wear Rogers hat with 2 of them being potential PK candidates whose hype is above anyone else in the series. Needless to say that the pirate king himself entrusted his hat with Shanks. If it is not same as him getting better portrayal then I don't know what it is. Apart from stupidity , he's pretty much shown to be same as Luffy and Roger in every possible way.
With the latest info we received about Kaido, it should be obvious for anyone that words are useless against him and that he's not level headed. So if anyone gets in his way then he'd attack them without a second thought even if it's a yonko. After all he insane enough to attack enemy groups all by himself. Shanks managed to stop that guy from going after Whitebeard in no time and actually managed to reach MF to stop the war. Once again if it is not portrayal then I definitely don't know what it is.
About Big Mom: If it isn't for the sake of argument I am pretty sure even you'd admit the fact that male dominance is too high in the series so she can't possibly be stronger than fellow Yonko. And nothing surrounding BM actually hints the point of her being stronger than any other Yonko. She doesn't have anything to offer when compared to others so putting her above others is just stupid. And there is nothing wrong with putting someone above others based on what we have given so far because that's how arguments are being presented in this kind of discussions for ages. It's not like we know everything about every single character in the series yet we tend to discuss stuff about them.So there is nothing wrong with making conclusions based on what we have in our hands. But they can't be presented as facts , I can agree with that much. Shanks isn't conformed to be stronger but with what we have seen so far he mustn't be below Big Mom or BB. That's what I have been trying to say.