Based on your responses to comments, I would say to eliminate Oahu. I lived on Oahu for several years and I love it, but it is not what you are describing as wanting for your vacation. I also am not a fan of Ko'Olina. It is wonderful for those who want to swim without fear of getting pulled out to sea or want Oahu without the urban noise of Honolulu/Waikiki, but it's not a fit for your vision of vacation.
I would break the remaining choices into these sub groups:
Kauai- you know you loved it and would be going back to re-live happy memories and try new things that have become available or that you missed. Traffic can be bad in parts of the island, but some of our most distinctive and most magical Hawaiian memories are from Kauai. If you feel in your hear that you want that vacation again, then go have it again and don't look back!
Maui- time on the beach is the big draw here. Beach walks, lots of sandy beaches to sit and relax and look at the stunning water, opportunities to take boat rides out for sightseeing so you can be on the water without the physical effort. This is available at any island, but Maui I feel shines in this area. The negative to me of Maui is any "drives" are typically very crowded with other tourists. It is our least favorite island to go "explore" with open agenda, so if driving around to sightsee is your goal, this will need to be carefully considered. On the other hand, you can book a tour to just about anything you can imagine doing and let someone else drive. Also, the longest line we've ever waiting in at a car rental was in Maui- nearly 2 hours! My bestie and her family and my brother and his family love Maui, but they spend nearly all their time at the beach and resort.
Big Island/Hawaii- I think this is a strong contender for you if you decide to do something "different" from Kauai. The Marriott resort is the only true beachfront resort that I'm aware of on the island and leads down to A-bay beach. As beaches go, its very rocky and natural and smaller, but my husband and I enjoyed walking there as well as walking around throughout the Waikoloa lava rocks paths. It is located in a "resort complex" complete with shopping centers and restaurants, so that aspect is not very natural at all, but you see so much nature around you, mountains, lava rocks, beach. Also the boats to go out into the ocean all leave from A-bay beach, so that is very convenient for water based exploration. A-bay is a gentle beach so I think you could swim comfortably there if you choose. This is the island where you would be able to hop in the car and see where the day leads. You could explore many farm markets, crafts pop-ups, the volcanos, stargazing, black sand and green sand beaches, lots of history. The black sand beach is especially something I could see you enjoying as it is a very walkable beach and easy to park and walk to and along. The green sand I would honestly skip for you. I could see you enjoying a day in Hilo. But know that the Waikola area, where the resort is located, is the lava rock side so it's not the lush garden of Kauai. You can get to that quickly in a car ride, but it won't be right outside the door.
I hope this helps you decide what is right for your vision of the trip.