Meh. GGP has closed most of its roads to cars on the weekends for decades. Only the main roads to the museums were still open, and they were usually filled with drivers dangerously looking for a precious parking space instead of other road users. The city can pull rank and offer all the shuttles and Muni transit trips to the museums it wants to and still keep it closed to private motor vehicles. That the first reaction is to bemoan the lack of private car access is telling.
This is something many people wanted and worked towards for quite some time. I’m glad to see some progress on it. There’s really no reason for cars to be there. The whole park is quite accessible from the periphery and main parking structures will still exist for cars to come in/out of the park. A shuttle van or a trackless train type shuttle would be perfect for the park for people with limited abilities.
Map of the roads open to cars in GGP:
https://sfrecpark.org/ImageRepository/Document?documentId=16434
And a map of parking available to cars in the park:
https://sfrecpark.org/ImageRepository/Document?documentId=16435
The idea that car access is in any reasonable sense restricted is laughable. They have a 800 car garage directly connected to the museums.