I am not suggesting they close the playa, I am suggesting that they block the road a short distance back so that people can't drive on it and they don't steal the rocks. For the access issue they could put a gate in and have it open (with a ranger there) on a schedule so that folks with mobility issues can also see it. Another option would be to start a permit system like in Canyonlands - I think people would be much less likely to break the rules if they know that the rangers knew who was there and when.
My understanding is that this a truly unique feature (maybe I am wrong on that) where scientists have only recently been able to explain how it came to be. Unfortunately this is not a one off incident, the rocks have been moved, and some have been stolen, people have hiked out on it when it is wet, there are older vehicle tracks etc. What are other ideas about how these areas can be protected?