It provided a very loose-sketch core setting which supported all the existing features, giving them functional thematic roots.
It did not reduce all of D&D to only one or two settings. That was never the goal of Nerath...nor the result. So...yeah I just don't agree in the slightest.
Making a single example setting, so folks can see stuff in action? Sure, that seems pretty reasonable. But a big part of the problem with doing that is that it's (demonstrably) hard for the designers to see what setting would be implied by the rules they've produced. I don't know why that's such a problem, but it clearly is. Eberron could not have been created until after folks knew the 3e rules and their...foibles, shall we say.
But creating One Setting To Rule Them All and telling folks that homebrew and such isn't what the game is for? Absolutely not. And yes, you did draw that distinction:
No homebrew settings. No alternate-take settings. No steampunk. No Eberron. No Dark Sun. You were very specific about "countless homebrew" being a problem, not a positive.
There will be one setting--or maybe two if they absolutely must--and nothing else. I'm sorry, but that's simply not going to fly.