What King is saying is not to avoid writing darlings, but rather to remove them from the final product. This is important because I believe that breathing life into those “darlings” is one of the best ways a writer can improve his craft.
I think that Stephen King is a good author-ly voice to heed. He certainly knows how it’s done–he can buy all the groceries he wants, now! In fact, I think he’s hit the nail on the head. The nail is the problem, of course. And King might have been defining success, but I believe he’s actually defining the issue many aspiring “writers” face: bein’ considered legit. Street credit, if you follow.