Man in the Funny Hat
Hero
This is essentially what the OP feels the game has lost. When it began it was loose, open and BY DEFINITION reliant upon DM additions, interpretations and alterations. That WAS the game for the DM - building YOUR world from the mere framework suggested by the rules.Much of the essence of the 1974 OD&D lies in this: its essence is that it has no essence. By which I only mean that the barest skeleton is provided, and each Referee will judge it differently. Supplement I: Greyhawk is only the Gygax house rules; other supplements by other authors could be their house rules. The OD&D of Mercurius will be different from the OD&D of Korgoth. And that is how it should be.
According to this hermeneutic, D&D started to morph into something else with AD&D, when Gary's house rules started to become a standard, and the game was considered open to tournament play. OD&D (1974) is not amenable to tournament play... it could be played at a convention, but each Ref will have his own house rules. He must have them, because without them there is not a useable game.
Yes, Gary's "house rules" did become the default but honestly it did little more than bolster the framework and nothing to inhibit DM's from folding, spindling, and mutilating that framework at will to still make THEIR world from that framework. Hell, Gary himself never used a lot of the rules that were provided in AD&D and never really wanted to include them - he did so to please others who DID want them. But the game remained the DM's to reinvent as they saw fit, just as Gary himself used his own set of house rules layered onto his officially printed AD&D "house rules".
What eventually happened, particulary with 3E and 4E is that well-meaning, clever people with experience and understanding of GAME DESIGN began to... DESIGN the game. They removed as much of the need and desire to "fill in the blanks" as they possibly could. Game design principles suggested to them that the game should be PRESENTED in as complete a form as could be managed. A form that required the least amount of additions, interpretations, alterations and deletions. A set of game rules that neither needed nor wanted to be messed with.
I agree with the OP that doing so was a significant mistake. I firmly believe that this was facilitated by the fact that WotC was a company which at the time of acquiring the D&D game was wholly oriented around M:tG and Pokemon - card games which lived and died by RULES. Hard-coded, officially designed and sanctioned and deemed unalterable and graven-in-stone by everyone. It was this understanding and approach to GAMES that was brought to bear upon D&D.
Don't get me wrong - to SOME extent this kind of cleanup and standardization of such loose, haphazardly-assembled rules was desperately needed. What was NOT needed (and what the OP feels is missing) is that over the next decade the company publishing the game would handle it, and its rules, in the same manner as they handled their card games. They treated the rules as officially sanctioned, unalterable and graven-in-stone. Never, ever, NOT ONCE since they have acquired D&D has anyone in an official capacity said that the answer to ANY rules question is EVER to just do what you want. The response has always been "DO IT THE WAY WE TELL YOU." Oh, they're not Nazi's about it, they're just earnestly approaching the game the way they think they should.
The tragedy is that they're dead wrong. And THAT is what's missing.