Innovation as an artistic value did not exist previous to modern times, and by modern I mean modern industrial societies. I'm not saying art did not change, but it was in slow increments. An artist, novelist or poet deemed great was basically expected to just be great. With age, a certain maturation of style was expected, but nothing revolutionary. Was Shelley considered an innovator? Certainly not. Was what made Shakespeare great his innovative recasting of the genre? Not in the least. So what was it? Genius. Yes, not everyone agrees that all of the "greats" were talented, but that's the nature of humanity and the mystery of great art. Something is going on that we cant quite put our finger on.
Style, technique, form, character, dialogue, etc is what we're talking about. How an artist was able to mold and use forms to their own vision was what made them great. Now, two very important things happened to change peoples conception of art. One, the industrial revolution, and two, Marxism. Now just hang in there and everything will become clear. With the advent of the industrial revolution, the ideas of the marketplace became a philosophy to live by. To be static was to be dead (as you lost your place in the market to some new up and comer with fresh ideas). The goal of any new business person was to find a niche in the market that had never been exploited. Innovation became the ultimate watchword for greatness. Turnover could be quick and fortunes could be won or lost in a matter of weeks (then days, then hours, then minutes). With the industrial revolution there also came a new market. The proletariat. Yes, they were exploited and overworked, but over time many began to accumulate money. So emerged popular culture. Remember, art previously did not care for the masses. It catered to a few highly educated and privileged members of society and was not at all ruled by any market dictates. Onward....
People often lament the fall of literacy and the shortening attention span of the average person, forgetting the fact that mass literacy did not exist until relatively recently. The masses, even those of western nations who are for the most part literate, have not been schooled in epics, or poetry, or fine art (the debate as to whether this is a good thing is for another time), and therefore have a lesser interest in "great" literature with its innumerable classic references, and joys that emerge over time, rather than instantly. There never has been a nation of great readers schooled in the classics with overlong attention spans. So anyway, given that the proletariat and the emerging middle class had to be marketed to, so came the pulp novel, the romance novel, popular music as opposed to classical. And with the emphasis on the new and unheard of in the marketplace, what better signifier of greatness in the world of the arts where the emerging audience had neither the time nor the inclination (for the most part) to absorb art over the long term, than to worship innovation and make it the ultimate signifier of great art.
Now, lets back up a bit. The writings of Marx were on the minds of every intellectual in Europe (and elsewhere) in the late 1800s. In his writings, the ultimate enemy was the middle class, or the bourgeois. Exploiters of the common man, enemies of freedom and gatekeepers of intellectual thoughts and ideas, the bourgeois became the ultimate symbol of the comfortable, civilised oppressor. Since the arts in general were made or sponsored by the upper classes (and the emerging middle classes), then it was only a small leap to think that the artistic ideas that the bourgeois cherished (form, plot, dialogue, technique, etc) must in some way be false and indicative of oppressive ideas. Beginning with modernism, art began to throw off what were seen as middle class shackles and explore other territories. Picasso is the best example, but is a dangerous one because the man was extremely talented and for all his explorations was still ultimately concerned with form and technique. From modernism of coarse came post-modernism, and with it a rejection of form, technique and even basic artistic talent. Craft and ability were viewed with suspicion, indicative of some kind of comfortable bourgeois thought process. Art became about art, and about what art was (hence the last refuge of bad art became "At least its creating a discussion", thereby removing any aesthetic purpose from the art, aesthetics being a middle class pass time. Art must be instructive, utilitarian, "Great art makes you think", all sorts of tired, anti-beauty modes of thinking emerged. Beauty itself was seen as a bourgeois pleasure that the masses should reject). Important European thinkers (Foucault, Barthes, etc) derided "bourgeois" modes of expression as lulling the reader or viewer into comfortable, middle class thought processes (while also assuming that people were unaware that the artist as an individual was a result of the genetic and societal forces that shaped him or her). Art should (supposedly) free the proletariat, cast off the shackles of bourgeois thought, make people see "reality" for what it really was. In short, it should be anything but a skilled piece of work carried out by a talented individual. That reeked of middle class mores, exploitation of the masses, sexism, racism, and Christ, everything wrong with the world. Art attacked values. That became its very purpose, so much so that people believed that this had ALWAYS been the purpose of art. With enough of this kind of art, we could have a revolution!!!!???
The irony is that this left-wing anti-middle class thinking collided head on with market values implemented by the emerging middle class (and established upper classes). Suddenly enjoying anything more than 10 years old was somehow indicative of stodgy, bourgeois ways of thinking. Everyone had to bow down to the new, the innovative....because really, how else do you keep the attention of thousands of people with short attention spans other than telling them that this NEW THING is so NOW and REVOLUTIONARY that in order to be considered a NOW person you just had to own it. As a result of these two powerful forces merging, we now have an art world that doesn't value art. Ideas are seen as the most important thing (what is the concept behind the piece of art?), just as in the business world. We convince ourselves that if we understand the concept behind a work of art, the art itself must be good and that we therefore enjoy it. Art exists on the surface level, doing nothing but making points about art ("This redefines what we think of as art"....one more yawn). Aesthetics, talent, form and artistic ability are scoffed at, somehow being indicative of dullness.....oh god, you have a craft???? Society revels in the shallowest waters that art can exist in and we wonder why the music that makes lists year after year are not cared for five or ten years later. (Though we are at the point now where many people are thrilled to be reveling in cultural shallowness, but this is part of the emergence of a modern persona that combines ironic distance, showy displays of affection for kitsch and non-highbrow creations and an unwillingness to apply critical thinking to anything, unless it's people criticising their shallow tastes or not sharing their "awesome" approach to life).
Understand, I'm not saying there's anything inherently wrong with innovation. Its just that you can't enjoy innovation 10 years later. You can only talk about it and remember that this was once on the cutting edge. Unless there's genuine talent beneath any work of art, then it will die, and quickly, though among the intelligentsia, unlistenable, unreadable and just plain banal works of art are given life support thanks to the concepts that the art supposedly embodies, or how our bourgeois/commercialised (depending on who is criticising) sensibilities cannot handle being "challenged" by works of art that are "ahead of their time". To repeat, innovation, in and of itself has zero aesthetic value. What it does have is market value and cultural currency. Art, until fairly recently (and everywhere else in the world right now not culturally invaded by market principles) was nothing to do with innovative ideas. It was about the aesthetic pleasure given to the listener, reader or viewer. To be honest, I'm not sure there's anything we can do to change things now. Concepts and business-think rule and our arts are the worse for it.
As a postscript I'd like to add that Steven Moore makes a pretty good case for innovation being an important catalyst in the history of art in his book "The Novel: An Alternative History". I found myself rethinking many ideas as a result, but I still stand by the basic premise here.