The MCU simply has more durability on account of each facet is covering different ground. Iron Man is action movie fare, Thor is fantasy, Captain America political thriller, Guardians of the Galaxy space opera, Doctor Strange covers mysticism, and so on. Star Trek, is about a spaceship with variations on the theme, such as being 100 years in the past or the future, the ship being lost, a space station instead of a ship, and still a ship, but rather than the captain being the ship's lead it's a convicted mutineer on work release.
Also, the MCU isn't deliberately limiting itself by trying to adhere to the creative "vision" of a mentally ill alcoholic who has been dead for over twenty-five years.
Also, the MCU isn't deliberately limiting itself by trying to adhere to the creative "vision" of a mentally ill alcoholic who has been dead for over twenty-five years.