So the game would constantly build up to awesome boss fights, then not let you fight them? You just sit there and watch Snake be more badass than you could ever be.
I've figured out the premise of MGS5. The Raiden in MGS4 was actually a Raiden clone created as part of the Les Enfants Ninjas project, and it aged really fast due to FOX-DIE. In MGS5, you'll play the real Raiden as he takes on Ninja Raiden, all while finding more reasons to be whiny and unliked by the fanbase.