Jack (John Holbrook) Vance (San Francisco, August 28, 1916 - Oakland, May 26, 2013) is one of those authors whose influence is felt, but it's sometimes not admitted or openly spoken.
All influential artists have followers and detractors, but Vance is one of those few that have no open enemies or anyone trying to "subvert" them. There are anti-Conan characters or anti-Tolkien writers, but I don't know of anyone trying to improve, correct, or subvert Vance. Why would anyone do that if his successors and imitators are still attempting to write like him? For similar reasons, I have yet to find someone saying, "Vance? Yeah, I've read him. Meh, nothing especial, really. There are dime a dozen like him."
That cannot be because he is an unknown author. Sure, he isn't as popular as others, but he wasn't a two-bit writer either. During his life, he wrote around 60 books, received multiple awards, and those who knew him had only positive things to say about his work and style. My guess is that he is one of those hidden giants whose presence is an intimidating force. Something magnified by the fact that he always tried to stay out of the spotlight.
Although there are strong and passionate communities of Vancians, most sff fans probably know of him indirectly, through the influence he had on Dungeons & Dragons. Perhaps they have also heard about his Dying Earth books and their baroque language.
In the famous AD&D Appendix N, Vance was one of the authors that had the "et al." abbreviation, meaning that Gygax believed all their works were important as a source of inspiration. But even that would downplay the importance Vance had for Gygax, as this article he wrote in 2001 shows:
"Need I say that I am not merely a Jack Vance fan, but that he is in my opinion the very best of all the authors of imaginative fiction? Well I am and he is!"
Gygax, mostly known as a game designer, was probably the most open and public about his awe and debt to Jack Vance, but he wasn't the only one.
This excellent article, The Genre Artist, by Carlo Rotella, dedicated exclusively to Vance, also mentions many other Big Names who became immediate fans of Vance the first time they read him. These include Dan Simmons, Neil Gaiman, Tanith Lee, and even a young Ursula K. Le Guin is mentioned. And these are the ones who are open about it. Truth is, the fan letters sent to him were probably full of (now) famous rabid fans sending him their undergarments.
To reiterate, when I say "fans," I don't mean just people who "like" him:
"Among them are authors who have gained the big paydays and the fame that Vance never enjoyed. Dan Simmons, the best-selling writer of horror and fantasy, described discovering Vance as 'a revelation for me, like coming to Proust or Henry James. Suddenly you’re in the deep end of the pool. He gives you glimpses of entire worlds with just perfectly turned language. If he’d been born south of the border, he’d be up for a Nobel Prize.' Michael Chabon, whose distinguished literary reputation allows him to employ popular formulas without being labeled a genre writer, told me: 'Jack Vance is the most painful case of all the writers I love who I feel don’t get the credit they deserve. If ‘The Last Castle’ or ‘The Dragon Masters’ [both are in this month's anthology] had the name Italo Calvino on it, or just a foreign name, it would be received as a profound meditation, but because he’s Jack Vance and published in Amazing Whatever, there’s this insurmountable barrier.'
Vance may not have been a proper pulp writer (his style is too unique, and his first published story, The World-Thinker, was written in 1946) but the curse of being considered a low-brow writer followed him, as it inevitably does to anyone who writes "fantasy" (writers of "magic realism", whatever that may be, are forgiven.) Not that he seemed to care, though. In fact, he probably liked it that way.
One of the most obvious traits of Vance's work was his distaste for fame, attention, and blowhards of all kinds. People who live in mental castles of their own creation are routinely mocked in his stories, perhaps because he knew he could have become one of them. From the Jack Vance's biographical sketch at the Vance Museum:
"'By the age of 15, I had read ten times the books an average person might read in a lifetime. [...]
Vance entered high school at age 11 and graduated at 15. He described himself at the latter age as bright, arrogant, introverted, and lacking in social skills. Then his grandfather died, the family was broke, and it was the bottom of the Great Depression. College plans were set aside and, for the next several years, Vance ranged the state of California, working at a wide variety of jobs: fruit picking, canning, construction, surveying, bell-hopping. He described this period as a metamorphosis: “Over a span of four or five years, I developed from an impractical little intellectual into a rather reckless young man, competent at many skills and crafts, and determined to try every phase of life.'”
I wouldn't describe that as "anti-intellectual" stance, since Vance stories have many deep intellectual themes, but these are seamlessly weaved into the story in such a way that many readers believe they are just enjoying a story of simple, pure, and unadulterated adventure. And that's probably one of the best compliments anyone could say about a SFF writer.