I ran a game of D&D 4th edition shortly after the books were released, and I badly mangled that abortive campaign.
I want to say that the books made me do it, and I have good reason to think so, but the blame is mine for letting them. Let me explain.
If you're a roleplayer today you probably started when you were a teenager. Not even an older teenager, but probably around 13 or 14 years old. Kids, really. That's when I started running D&D. The funny thing about ageing is that you gain experience. The thing about having experience is that you constantly use it, and understand the world through the lens of a great big pile of lessons hard-won. This, by itself, has the power to utterly destroy the imagination, if it's allowed to.
Our imaginations were on fire when we were young, and the fires are now banked, under control, and burning evenly for our adult use. As such we're much better at perceiving with accuracy, say, what's in an RPG rulebook. What we're less good at than we once were is filling in the blanks with utterly creative nonsense.
I assert that the enjoyability of D&D (in its various incarnations) is not due to it being a good system with good settings. Rather, it is just enough mechanics and evocatively-colourful setting to inspire that kind of fertile imagination that is endemic to young adulthood.
That game of 4th edition D&D I ran, I ran by the book. I believed, from previous experience, that I could just run D&D "as written" and it would be an enjoyable game. This belief set me up for a really disappointing series of games, though. 4th edition is bare mechanics with a few impurities called "flavour text" that don't really amount to a consistent assumed setting. The mechanics are all about how to vanquish obstacles and thereby get the mechanically-quantised character advancement objects (levels and magic items). There's nothing explicitly provided for creating good stories, immersive simulations, or satisfying game-type challenges. Since I was running the game "as written", none of that came out in play.
I'll say that again: RPG books are incomplete, and not nearly as full of awesome as you thought they were when you were younger.
If I'd been younger, I'd have automatically thrown in a whole bunch of things in addition, and it would have been lots of fun. I would have done it because I would have believed that "that's how the books say to play the game", but I would have been wrong. The "awesome" always did come from us, the players, not the game.
Having quantified knowledge of RPG theory makes it clearer to me when a gaming element isn't an explicit part of a rules set, but it also means that my intuition is inhibited from filling it in. Now that I know "better" as a gamer, there's all kinds of stuff I don't get for free anymore.
On the plus side this means that I have better tools to create a consistent quality of play for myself and those who game with me. When I was younger I had those sessions that "just sucked" without knowing what went wrong, which were all too frequent in among the awesome sessions. Having critical knowledge of how we create play is a tool I wouldn't trade away, but it does mean that I need to be conscious, in a way I didn't need to as a young GM, of how I develop the fictional elements that makes everything else fun.