I think Sanderson's case is different. Unlike Anderson is he is intelligent and a good storyteller, though since he writes in secondary worlds with some scope, he would do well to learn to take a step back from the action and actually look more into the characters, the setting and the issues in his secondary worlds. It's not something unique to Sanderson. The present generation of Fantasy writers differ in one crucial way from the likes of Tolkien, Lewis, Kay, Jordan, GRRM etc. Fantasy used to be a genre where the best writers were men and women who had seen and experience the world, met tons people from various cultures, lived a bit, quite often had seen horrors and war firsthand - often they also had decades of reading about anything or everything, or actually working in intersting fields - and then they translated all this into a rich, fascinating secondary world. Nowadays, it tends to be written by very young 'professional authors' who often studied 'creative writing', have grown up loving Fantasy and reading in general. They are creating their worlds, their cast of characters, the issues in their story not from the heart and experience, but from book knowledge. It's exceptional for people so young to have enough experience, have had enough relationships of all kinds (or witnessed enough of other's) and a personal enough perspective on the world to be able to translate this into good fantasy. This is a bit what I see in Sanderson. He has obvious talents, interesting ideas. He will probably be a great writer when he's a bit older, but he might want to slow down writing and get out of his Utah basement to live a 'real life' a bit. KJA is a bit like that too - there doesn't seem to be much more to his lifestyle than writing, reading, hiking and promo tours. Worse, his wife is the same. If we look at the greatest books of SF/Fantasy - those that stood the test of time etc., that's not exactly the sort of situations from which they arose.Never really considered it from that angle before, but after reading it, I have to say that I've noticed that many of the authors that I enjoy most today (among them, M. John Harrison, China Miéville, Jeff VanderMeer, Gene Wolfe, Ursula Le Guin, Jeff Ford, Michael Moorcock) all have had something interesting in their backgrounds, whether it be being exposed to various cultures at a young, impressionable age, or working at some interesting "blue collar" or experimental labor jobs, or working in publishing/editing at a young age, or just participating in what today might be called "extreme" sports. Regardless of their disparate approaches to writing, one thing that I've learned about each of these authors (and several others) is that, as the quoted bit alludes to, each has "lived a bit" and experienced something in life that might be a bit "unusual" or at least would hold some sort of influence on their perceptions of life and how to write fiction.
But does the inverse hold true? Is "book knowledge" really a pale substitute, or does it too constitute some sort of positive influence on the creation of "meaningful" fiction works, especially those of a speculative nature? What do you think? Who would you cite to support your point of view?