Thor: The Dark World represents all of the MCU's worst tendencies: shoehorned humour at the expense of good scenes, a cookie cutter underdeveloped villain, and an over reliance on big outlandish explosions. It doesn't help that the story is also convoluted and lame, made even worse because it introduces the second infinity stone.
All in all, Thor: The Dark World is not a terrible movie. It's just far more cliché than its predecessors, and that's disappointing.