A good compromise would be having a game designer with a maximum amount of knowledge about all the aspects involved n making a game and a team that only suggests things to the main game designer but lets him process what they tell him and use it as he sees fit, without further discussion.
On a big budget game, a designer can't possibly have a maxium amount of knowledge about every aspect involved in it's creation... It takes 10 years to master a skill, and there's more than 10 specialists involved in the game, so this hypothetical designer would be long dead of natural causes.
In smaller games, sure, the designer can have his fingers in every pie -- this is usually how small 2/3 man projects are made, where the designer will know about every aspect because they are also one of the implementors.
It's only on really large projects that it's economically feasible to have a full-time designer (or several designers each with their own speciality).
Seeing that these designers can't possibly know how every aspect of implementation actually works, they need to defer some decisions to other specialists (that's the whole point of having specialists). As mentioned before, AI systems are a great example of this, but so are movement systems -- e.g. the first assassins creed had a team of several dozen people working on just the mechanics behind the main character's movement. There's no way that a single designer could sit down and theory-craft all of the details behind that movement controller that those two-dozen specialists discovered during their implementation process, up-front, without a feedback loop, into an immutable GDD.
someone with enthusiasm suggests how they think things should be and someone worn down by the industry talks beside the question by stating how things are.
I'm not worn down and trying to erode your enthusiasm, nor trying to talk beside the question. There are a lot of reasons for why it's a general consensus that an initial idea does not have much value, and also why this stereotype exists, which we're trying to explain.
Implementing someone's game ideas necessarily requires creativity on the part of the implementer. The design given to an implementer is necessarily vague, otherwise it would already be an implementation and not a design! Implementers are not just a tool to be manipulated by a GDD, but an active participant in the design process, being guided by the game designer.
If they are a tool, they are a tool that is necessarily in a conversation with the designer, guiding his hand while his hand guides it. A great artist is one that can use his tools well, so a great designer is one that is a master of conversation with his tools.
The fact that you disregard this participation as meddling, robs you of the ability to understand the implementation process and the role of a designer in it, so there's nothing much we can say here.
No, it's just a valuable game. Publishers would pay a lot of money just to own that name.
If a thing is worth what someone will pay for it, the Call of Duty series must be the epitome of gaming.
FWIW, even bland, generic, middle-of-the-road games like COD require talented designers. Even just getting a bland game out the door, complete in it's bland vision, on time, requires a large amount of talent. It may be a different kind of talent from the ones that produce the cult-classics though. A real visionary and critically acclaimed designer might actually be a failure if required to produce intentionally bland blockbusters Everyone has their niche.