The Witcher 3 is a massive single player game, like Skyrim and a great one at that. It's a genre that I am really into and can consume me, they just envelope me in its world and lore. Destiny is a always online FPS game with limited social aspects. I would in no way call it a MMO as it doesn't fill that criteria. The main draw is its spot on FPS mechanics and rewards, not it's story (story?) or its world.