LOTR was written against the backdrop of Hitler, Stalin, Mussolini, and a world where good and evil didn't seem very ambiguous, yet think about how many times this ambiguity comes up: Gollum. Good or evil? Saruman? Boromir? There is nothing childish or "Pooh-like" about these characters. They are very real, very intense confrontations with good and evil. Even Bilbo and Frodo themselves struggle with this. We assume the ring has the power to corrupt, but is the ring truly doing the corrupting, or is this lust for power something innate within that the ring simply exploits for its own purposes?
And what defines true power? Is it the ring itself? Is it the one who carries it? Frodo and Sam, two of the smallest of the races of Middle-Earth manage to bring down the most powerful of enemies with little more than courage and a desire to do what's right, while the powerful (the humans of Rohan and Gondor) quibble amongst themselves and their leaders are easily manipulated or go mad with sorrow and fear.
Long story short, I think Moorcock is wrong. I find the idea of a drug-addicted elf more ridiculous than anything Tolkien ever wrote. It's as though Moorcock defines fantasy as merely a setting through which he can play out his literary amibitions. That isn't to say there's anything wrong with a drug-addicted elf, it's just that drug addiction -- a so-called "real" problem to Tolkien's alleged "Pooh" problems -- does not alone elevate one's work to higher stature, nor should it be used a bludgeon to demote the work of others. I have learned far more about life and human nature from Tolkien than I have from Moorcock, and Tolkien's work was more entertaining too.
EDIT: Oh, and if you want to read some incredibly clever and unique sci-fi/fantasy, check out anything by Gene Wolfe or Jack Vance. Wolfe's Book of the New Sun is brilliant, and Vance's Lyonesse trilogy is amazing.