By comparison, a bad story (let's call this hypothetical bad story Final Fantasy 13) introduces new concepts at a breakneck pace early in the story, rapid-firing made up words at an audience who has zero information about the world.
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The more "out there" your world is, the longer you need to take establishing it. The more new concepts you want to teach your audience, the more carefully you need to pace the teaching process so that they actually learn what you're teaching. Final Fantasy 13 dumps you into the world, expects you to hit the ground running into an action sequence, throws a sackfull of fuzzy terminology at you, and then later on decides that if you want to enjoy the story you need to read War and Peace for a while.
With FF13 I think SE's hubris got in the way: they assumed that players would all have been on their hype train for several years, watching the trailers, playing the demo, reading all the pre-release materials and "light novels" and all their other little money-grabs.
(I had actually done this -- the pre-release stuff made it look like the game was going to be amazing -- so I had no problem understanding things. But someone new to the series or to the game would be totally at sea with all the concepts, let alone the vocabulary.)