One of Mies van der Rohe’s pupils, a girl, came to him and said, “I have difficulty studying with you because you don’t leave any room for self-expression.” He asked her whether she had a pen with her. She did. He said, “Sign your name.” She did. He said, “That’s what I call self-expression.” (John Cage, Silence [p. 269])
A while back I wrote how no author can help but express themselves. I have to revise that a bit in light of what I just wrote here: no author can help but express themselves as long as they have the means to do so.
I've repeated this before, and in enough variations, that you are almost certainly sick of it by now and want me to move on to something else. But I hammer on it often because it is one of the things I see being most consistently wrong with many of the budding (and not-so-budding) authors I run into. They equip themselves to create copies, or copies of copies, but not something where the unmistakable hint of the author's persona comes through. To use a phrase I always loathed, because it was almost always used in a thoughtless way, they are not expressing themselves.
The most damning thing that can be said about a book is that anyone could have written it. SF&F, and modern genre fiction generally, too easily devolves into a custom-built receptacle for such writing. When there is talk of being original, it's mostly in terms of this or that clever idea for a story, not in terms of an outlook, a philosophy, or a point of view. Dwight Macdonald's talk of Masscult comes back to mind: it wasn't writing for the masses he objected to, but writing indistinguishable from the masses, writing where the self being expressed evinced no power of spiritual dissent.
Word choices are not what sets one author apart from another. It's what they see in the world and what they single out when they report back on it. Nobody conflates Dostoevsky for Dickens; nobody mistakes Heinlein for Asimov; nobody confuses J.G. Ballard with Douglas Adams. You couldn't mix those guys up if you wanted to. But I'm hard-pressed to say how, oh, Daniel H. Wilson and Max Brooks are distinct from each other philosophically — not in the sense that their books are no good, but that in them I rarely get the sense their work comes from a place of great urgency and personal fire. (I may find Neil Gaiman terribly hit-or-miss, but I can't say his work isn't personal.)
Self-expression is not the same as self-indulgence. It is seeing what only you are empowered to see, in only the way you are empowered to see it.
The more we surround ourselves with writing not borne from self-expression, the more we take such things for positive examples: after all, look how many copies of this one sold, and how that one got optioned for a movie, etc. They Must Be Doing Something Right.
SF&F is satisfied, too satisfied, with being original in just its plot or its story trimmings. This explains the prevalence of "X plus Y" writing in the field; the latest formula of Add Steampunk To X hasn't yet completely run out of, um, steam, but it's getting mighty wheezy. It's easier to allow the originality in your story to stem altogether from the fusion of existing recognized pieces than it is to have it come from somewhere personal. And maybe more marketable, too, since it's always easier to sell a concept than an outlook.
None of these things are specific to SF&F, though — they're by-products of the way fiction is commercialized. They make it tougher, although far from impossible, for original work to prosper on its own terms. And this isn't wholly bad either — a totally original work, with no connection at all to its moment in time and with no discernible inspirations, would probably be all but unreadable. A balance is required. But there are few checks left in place to ensure such a balance, what with literary criticism (especially of genre fiction) a ghost of its former self, and trend- and concept-based marketing bulking far larger than the cultivation of audiences. The author has to fend for himself in far too many ways. The few that get bootstrapped into the public eye by dint of commercial success find it somewhat easier to do so, since they already have a good slice of the attention pie — but once they have it, what do they do with it?
Final note. I imagine I am myself, and will continue to be, guilty of every single one of the sins I describe. I look back at the very work I am producing now and ask myself, does this break that rule? Does that simply make the problem worse? And often there's no way to tell other than to finish it, put it out there, and brace for impact. It is the easiest thing in the world to criticize everyone else's work, and all but impossible to do that effectively for your own. My neck is yours.