Robert, I understand the feeling. I too felt Oahu a bit crowded. It is not really an experience of Hawaii and is not that easy to get away to a place where there is no people.
What you say about the beaches. Well here in Maui I never felt they were not clean. Maybe it has got to do with the amount of people. I do see trash on some off the beaten path places. It seems it is too much of an effort to drive the truck all the way to the land fill and dump the trash there. Lots of people just dump where they feel is is ok. I really do not understand it.
What you say about galleries seems true but wait a minute, you have galleries there. As far as I know there is only one fine art gallery in the Grand Wailea Resort and most of the photographs that were there when I visited were of Hawaii, and very few of other places. Most peolpe here are turists or temporary residents. They want to take Hawaii back home. The other citizens of Hawaii don't feel at all interested in fine arts. Don't know what it is that there is such a small percentage of artists, photographers, etc. Just no interest!?!? Weird?