This is a problem I always had with people reading the story transversally.
They look at the action or thoughts of characters as if they were machines, thinking that One Piece is just another shonen were protagonist are supposed to understand each actions possible at every single moment and only making mistakes that we can clearly see and understand.
But again, this is not what One Piece is. One Piece is demanding in term of empathy and observations since the devil lies in the details. Without that, people will most of the time fail to grasp the subtilities of the behaviors, especially the mistakes of characters.
People are not shocked when Luffy does not recognize Usopp, its funny and it makes sense narratively, the same way, people will often overlook the fact that in Whole cake LUffy actually see through people (pretty much everyone). This is because narratively and humanly, Luffy was in seeking mode in this arc, much more empathetic, much more focused on the feelings of others and this is what allowed him to learn observations haki rapidely..... And yet, they do not take the time to step back and analyze the fact that this is exactly what they would criticize in the case of characters like Xebec or Whitebeard.
You need to read the story in context.
SOrry, who is Big Daddy Saran ?