I wrote a long reply about my trips to Hawaii and specifically to Oahu that were deleted.
So I guess I'll keep it short and sweet. Oahu has many unique cultural sites and is the most populous island. If you want to know Hawaiian culture Oahu is a great starting place with multiple museums and other cultural activities.
I can't believe someone traveled all that way (I'm from the east coast of the US) to say it was dirty and boring.
I don't think the OP researched her trip enough or maybe museums just aren't her thing. (Or beaches or fine dining, etc.)