We used the ship excursion to go to the Arizona. It included a bus tour around the city that was great. It cost $79 and worth it. On the other islands we did it on our own.
We heard from many of the people on board that they thought that the excursions were too expensive and too long. Many times that we took off on our own and rented a car we saw the same people as if we went on the trip with them. What we liked is we left when we wanted to and not set on the bus waiting for that one or two couples that,(I don't know how} did not hear what time to be back to the bus. That happened to us at the Arizona.
It is a personal choice but I think that the ship leans on the phrase, "if you miss the ship" to get you scared into taking the ship excursions. I can see it in a country that you have never been to or a trip that is too far or hard to find. Hawaii was not like that. Driving around there was no problem.
At most ports there were many private operators and nobody had any problem with them from what I heard.
Nobody was left behind!
We had a great time but next time will do a land trip to spend more time on one island.