In my opinion, it gets put at the feet of the DM as they are the crossroads of a social game in which they are the position of adjudicator. The game is what it is (apparently not a movie, story, or sombrero from some of the other threads around here). It is the people, both DMs and players, that either make it work or breaks the game.
Older editions of D&D put a lot on the shoulders of a DM - game world development, adventure development, rule adjudication (much more than today), and all the things needed in session. It is no coincidence that 3.x put more rules into players hands and 4e gave the DM better tools to make their adventures. It helped take the "swing" out of the DM play - today you are likely to have a more "fair" game under 3.x and 4.0 than when the rules were sparse (for example, I had very few house rules under 3.x vs. prior editions). There are still great DMs and horrible DMs, but I think the "average" DM is much better.
But having so much defined can have its drawbacks. For myself, I felt like 3.x put me in a box of trying to "find the right rule" for every situation. Having so much detailed out tended to push me to find the right rule ("its got to be here somewhere") vs. improvising where needed ("+2 bonus and move on!"). I moved on to Savage Worlds and just love the "freedom" for lack of a better word. I think that might be one of the reasons for the popularity of old schoole gaming - people can go back to a less defined ruleset with better adjudication from their experience from a more robust ruleset (pure hypothesis here, but I do feel liberated running something like Savage Worlds vs. 3.x or 4e)