Honestly there is a lot more to a sandbox as well but it’s all flavors of “off the rails” gaming. The more off those rails you are the more “sand-boxy” the game. The more player actions have lasting and relevant effects on the world the more sand-boxy it is. All that being said there is no perfect sandbox. There are always limitations of some kind but the closer we can get to a world that is fully interactive in which we can change everything, do anything, and be anyone we want the close we are to that “perfect sandbox”.