The captain is not addressed as “Mate”. That is bogan-speak. Same advice applies to the captain addressing the first officer. It is also shows lack of respect for each crew position.
I must admit that I'm a serial "mate" offender & had no idea that it was so offensive to some.
As a civvie I have never refered to a co-worker by their rank nor would I ever do so willingly. It's dehumanising at best and cringe-worthy at worst. Removing the human element in a command structure has it's place in a war environment but not in a benign airline cockpit environment.
Who in the hell was John Wayne, I hear you say?
He was the "Duke". An F/O who never took no sh
t from no Captain....Pilgrim.