He wasn't because, they can Cheap shot him thats the fact that you are make excuses about.
Akainu was afraid of Shanks like, " oh shit i will get rekt, let me become quiet, so he can see me".
Luffy is put on his level by Kaidou, i want to see his face when he face PK Luffy, he will shit his pants too.
Isn't you who saiyng that Luffy isn't a Top tier? While he is making another top tier attack been serious and saiyng he wasn't this serious since a long time.