I agree with Moogle and Barsoomcore that few, if any, of today's fantasy writers can match the great masters of the past...and I'm not some old, nostalgic fogey! Their prose is just plain better, though I understand that people's tastes will vary according to their preference for high-brow or middle-brow culture. I just finished reading Perdido Street Station (a modern book which has won awards and plaudits left and right) and was terribly disappointed, not by the world (which was very interesting), but by the story and prose. It was mediocre, and it seemed to reek of D&D. D&D needs to go back to the roots for some of its inspiration. I think the success of "originalist" books like Iron Heroes and Grim Tales attests to this.
As for Vance, if you want to see which RPG was most influenced by his work, try Talislanta. It's a wonderful interpretation of his worlds, without being a hack clone. The weird spell names, strange creatures, devastated landscapes, eccentric wizards and circumlocutious descriptions are all there.
I also agree that today's authors make magic too commonplace, and reflect too much the contorted politics, political-correctness and sensibilities of our times. They create bland, magic-suffused worlds that appeal to everyone and no-one.
I don't agree with the "high-magic/low-magic" dichotomy. I want my worlds to be dazzlingly high-magic and my characters/players solidly mundane; therein lies the adventure.
I think Howard, Leiber, White, and Glen Cook got it exactly right.
Last note: I blame today's educational system for the shortcomings of modern writers. The great masters had a far better classical education than any university is capable of today. Even as our sciences have gotten better, our humanities have degenerated in a horrendous fashion. That too, is a sad reflection of the politics of our times. :\