There's a very large and, I think, very important critical question about art I never see addressed; or at least, if it is discussed I don't know where and by whom. I'll give some examples of what I'm talking about.
Let's take a man (for example) in his 40s. As a kid he fell in love with the music of The Beatles, just like millions. But although some of what he responded to, in that music, had to do with the skill of Lennon-McCartney-as-popular-composers, much more had to do with the extraordinary potency of music itself. Nobody ever hears music in the abstract; we always listen to music embodied in one composition or another. The thing is: whichever musical text happens to be the one that introduces you to the wonder of music itself will tend to receive, back over itself (as it were) a lustre it has not in and of itself earned. Lennon-McCartney were a talented pair of songwriters; but they didn't invent music itself. A good proportion, I'd say, more, a majority of the emotional impact of their work involves them piggybacking on Music Itself. Another example might be: 'I used to think Robert Graves' Claudius novels were brilliant; now I see what I was reacting to was the fascination of Roman history; and Graves's novels are rather clunkily put-together.'
The problem is: how can a critic separate out these aspects of a work of art? It's a particular problem in SF, where the sort of short stories, novels and films that first blew our minds and introduced us to Sense-of-Wonder can shape our tastes, such that we prize works that imitate those earlier works, and we ignore their faults to the exclusion of other, better-written or better-made stuff. But as with Music Itself, 'the Sublime' was not invented by Asimov's Nightfall (or whatever); the 'Visual Spectacular' was not invented by Star Wars, and (to select one particular key text of my own youth) Narrative and Enchantment not invented by The Hobbit/Lord of the Rings.