Kidd wouldhave fought a bit longer if he knew how to use advCoC. Those that lack advCoC coating will be smacked when hit with it. Like Luffy was. When he learnt it, he went toe to toe and ultimately be the victor.
Yeah, now there's a good argument that Shanks might low diff Big Mom... Tbh, I always thought that no top tier can mid diff the other one but with this... I don't know how powerlevels are even debatable at this point. It makes no sense whatsoever.