Special DMs were no more common than special players in groups that were all learning the game together.
Let me ask this: Do you believe that there are multiple valid playstyles?
Even further, do you believe that a group that has a blast together is "doing it right" no matter how they are playing?
Yup, to both questions.
Does some game designer, regardless of talent, know better than you what is import in balancing the game for your play group?
Let me rephrase the question. Does some game designer, who has spent hours and hours pouring over the minutia of the system, possibly has education in game theory, and a wealth of background in the system in question know better what is important in balancing a game for my play group?
Absolutely. 100% yes. If he doesn't, why in heck am I buying his game? If I, amateur gamer who spends a couple of hours a week playing some game, can identify points of balance better than the game designer can, then that's one seriously piss poor game designer.
I would hope that any game designer is better at identifying the importance of balance in the system than I am.
Here's a mind blowing concept for you- thinking that game balance ought to be provided between the covers of a book is a form of one-true-wayism.
Possibly true. OTOH, presuming that a GM will "fix" the game is lazy design. I give older versions of RPG's a pass on this because, well, in 1976, I doubt that a lot of the concepts had really been thought of all that much. For the same reason I don't blame Ford for not including ABS brakes on a Model T, I don't fault Gygax for not including a skill system in the game.
But, thirty years and millions of hours of game play experience between D&D gamers? No, you don't get a pass anymore.
Think of it another way. If you rely on the DM to "fix" the game for his group, you are presuming that the DM has the ability to do so. You are, in other words, presuming a good DM. What percentage of tables have DM's with that ability? I don't know and neither do you.
How can you presume a total unknown?
If DM's capable of adjudicating in fun ways for their groups is 95%, then fantastic, presume away. If, OTOH, it's only 50%, then you've just told half the gaming tables out there that they are going to have sucky experiences because the designer couldn't be bothered to produce a complete system.
Is it still good if half the tables suck? How many sucky tables is acceptable? 25%? 10%? Wouldn't it be better for the designers to use the experience that they have accrued over the past three decades of game play to produce a system that is actually balanced? It might not be perfectly balanced, but, it's a hell of a lot closer than earlier D&D was.
It's true, you'll never achieve perfect balance, and, honestly, I don't think we ever should. But, shoveling off responsibility onto the unknown abilities of the GM is not acceptable anymore. We should know better.