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So SimCity, Rollercoaster Tycoon, Euro Truck Simulator, The Sims, etc aren't games either? Since they too are sandbox games that let the player direct the experience. Frankly I would love to know what your definition of the term "gameplay" is because it seems unique. To me any interactive medium contains gameplay mechanics, even point-and-click adventure games do, hell even some BluRay menus could be described as hav…
You can tell if you're doing well at simcity, rollercoaster tycoon, and the sims. (I don't know anything about euro truck simulator.) Zerg rush is all about how many zerglings you kill and how much of the page is still alive. In minecraft it's all about what you feel like building and there's no objectively doing well or badly. It's hard to make a thriving sim city, it's trivial to make a giant sculpture in minecraft…
That said, you can always play Creative mode and/or Peaceful difficulty if that's your style.