The implicit promise of a sandbox game is of endless and varied adventure but ultimately, players perform the same tasks, not just in one particular franchise of sandbox games but in all of them. They destroy enemy camps, ollect items, fight bosses and build upgrades, and it's all framed in the cold, numerical sense as progression.
What players do in sandbox games, essentially, is eat the world. Picking it clean of places and activities and people, growing fat off experience points and gameplay benefits in the process. What they're eating is fast food – it's always the same.