There are still parks like that. Our next trip is going to be a Universal-only trip and there is zero planning to do other than the hotel. Nothing. On a smaller scale, we went to Busch Gardens Williamsburg (which is a great park BTW!) and all we did is book the hotel room, drive down, and go to the park. We had a blast. No planning. Disney is just very special, for better or for worse
Harry Potter can still get crazy if you don't get there early.