I politely disagree.

I see a lot of people try to seperate the game from the world and it is an exercise in abstraction. I tend strongly towards simulationist design aesthetics, if not always playstyle, and efforts to escape the notion that the games rules actually some how actually mean something in the world always strike me as an effort at deliberate self-deception.
That does not mean that Sir Xe Elpam, Paladin of the Silver Tower, knows he has 76 hp, but it does mean that he knows a 20' fall holds little danger for him even if it's likely to kill his trusty henchman Patsy. He also knows that he can stand in a burning room for longer then he could as a mere stripling. What exactly those hitpoints represent in game (and the seperate question of what Sir Elpam thinks they mean) is immaterial next to the fact that they do mean something. They are not merely a storytelling abstraction or the Paladins increasing willingness to stand up to hails of arrowfire actually becomes the story of a heroes descent into madness as a lifetime of adventuring take a toll on his psyche.
Even from a narrativist pespective a game engine (The mechanical system of the game) is a device for story telling and like any good device it should be optimized for it's intended purpose.
So if you want to tell a fantasy story in the vein of Conan or Fafhrd, concentrating on valiant warriors fighting through hordes of lesser foes then a system like Iron Heroes or Riddle of Steel is the optimal tool. If you want to meddle in the affairs of Wizards then you should prefer Ars Magica with its rich and subtle magic system. If you want to concentrate on affairs of state and courtly romance then a system like Blue Rose or 7th Sea will serve you better. If you want to tell intricate tales of espionage and intrigue in a future trans-human body-jumping society then Eclipse Phase will serve you much better than Bunnies and Burrows.
At some point in game design you have to make choices. If you are not building a toolkit game like the Hero System, or a complete hodgepodge to the point of crossing a melting pot with a black hole like Rifts, then you will have to and want to make choices about the world you portray and the stories you want to tell in it. Sideplots in OoTS aside, D&D is a lousy platform for telling stories of 4-color golden age superheroics. It's also a lousy choice for corporate skulduggery in a high-tech dydtopian future. So you cut those choices out. If you don't see why I encourage you to imagine the flamewars that would ensue if 5es basic class lists included "Alien Star-god", "Cyborg Delivery boy", and "Chibi Pastel Equinette."
Good game design demands that choices be made and that the games focuses on some smaller goal than modeling "anything I can imagine." One of the primary aspects of any well written fantasy world is it's magic system and attendant cosmology. D&D is and has always been pretty sloppy about this and it inevitably gets worse as the edition wears on and class bloat sets in.
That having been said, they have an opportunity here at the outset of 5e to try and set some clear lines for what, if any, differences exist between Arcane, Divine and Psionic (and shadow and binder and truename and incarnum, etc, etc, etc, etc) powers and what those differences mean. Conversely if they lump "everyone but cleric" into a single umbrella class then that too has meaning although I would anticipate years of glorious internet nerdrage over what that meaning is, exactly.