Sunfish,
It's true that cruise ship staff are low paid and there is a reliance on payment of a gratuity at the end of the cruise. This structure of the gratuity and how it cascades down the ladder is explained to the passengers. It's an American business model although you can choose NOT to pay it. You can tip directly to those who have provided the service such as cabin staff, dining room staff,etc.but not the Captain or his crew as they are paid quite well and I expect in accordance with their responsibilities, i.e 3000 persons on board.
My experience has been different to yours as we had Indonesians and Philipinos most of whom spoke English and were treated well enough. If they did not meet performance KPI's, they would not get another cruise contract
I WOULD cruise again.
I'm sure Qantas management would LOVE to "drop and drag" some elements of this business model, but most is impractical to apply in this industry. An example would be that most crew live on the vessel for the duration of their contract being about 3 months at a time.
I don't see reliance on tips to get a reasonable return in the future, but contracts could be.