“Fantasy became as bland as everything else in entertainment. To be a bestseller, you’ve got to rub the corners off. The more you can predict the emotional arc of a book, the more successful it will become.
“I do understand that Game of Thrones is different. It has its political dimensions; I’m very fond of the dwarf and I’m very pleased that George [R R Martin], who’s a good friend, has had such a huge success. But ultimately it’s a soap opera. In order to have success on that scale, you have to obey certain rules. I’ve had conversations with fantasy writers who are ambitious for bestseller status and I’ve had to ask them, ‘Yes, but do you want to have to write those sorts of books in order to get there?’”
Emphasis mine. I've long felt this way about SF and fantasy, and writing generally. The cost of becoming famous, or a bestseller, is that you have to write the kinds of books that most everyone would want to read — in short, mass-market material. There's no end of people lining up outside the door to create such things. As for me, I decided a while ago I'd rather try and create something that couldn't have anyone else's name on it but mine.
One common comeback to this is the idea that if you learn how to write what's commercial, you can always find a way to put your stamp on it. I'm not sure I believe this to the degree that other people do, if only because all the things I find most interesting and worth putting in a story are, all too often, the kinds of things that get ruthlessly schooled out of mainstream work anyway — the corners that get rubbed off, as Moorcock put it.
The world we live in doesn't make, or permit, much distinction between bestseller status (a lot of people bought your book) recognition (a lot of people read your book), and validation (a lot of people liked/connected with your book). The first typically stands in for the second or the third, when it's the latter two that most authors really want. Most authors I've met are not so much interested in money — there's far easier ways to get rich — as they are in being noticed and being told they were onto something. And, no, I'm no different.