To be fair Tolkien fails hard at the economic, ecology and population dynamics level.The Forgotten Realms was created by an 8 year old American boy. At least that is when Ed wrote his first stories of it. He created the D&D setting at age 16 in 1975.
I think perhaps you give anyone too much credit for being able to produce a viable world that accounted for agriculture, commerce, etc at that age and in those years prior to the internet and the mass availability of knowledge that would allow such today. I know its fun to poke at Americans, but really, I don't think what you want could have been done by any child the world over in those years.
(And no, I'm not a fan of the Realms, but I do often run games set there because it is readily available and good enough setting for the feel that interests me.)