I think that's the message, that you can't be Pirate King without a good crew. A captain can be very strong, but without allies he won't get very far in the NW.
Luffy, Shanks, Teach, BM and Kaido all know this and each applies it in their own way. Luffy has people who stand out for their individual talents, as Aokiji said. Shanks has a balanced crew. Teach recruited the most dangerous criminals from ID and is looking for powerful DF for them. BM educates/trains her sons and daughters to increase the power of her crew. And Kaido is looking for strong subordinates.
It is no coincidence that the rest of SN do not have good crews. It is part of Oda's message.