Also see Stanislaw Lem's "Philip K. Dick: A Visionary Among the Charlatans"[1]

Compare Vonnegut:

"Yes, and now Putnam has published for the first time the full text of "Stranger in a Strange Land," by Robert A. Heinlein (1907-88), an abridged version of which has sold 100,000 copies in hard cover and nearly five million in paper since its debut in 1961. An enormous number of readers have found this book a brilliant mind-bender, and yet I doubt that Heinlein's name was ever uttered at a meeting of PEN or in the halls of the American Academy and Institute of Arts and Letters.... How could this have happened?"

to Lem:

"What the absence of such model works leads to is shown, more plainly than by any abstract discussions, by the change of heart which Damon Knight, both author and respected critic, expressed in SFS #3. Knight declared himself to have been mistaken earlier in attacking books by van Vogt for their incoherence and irrationalism, on the grounds that, if van Vogt enjoys an enormous readership, he must by that very fact be on the right track as an author, and that it is wrong for criticism to discredit such writing in the name of arbitrary values, if the reading public does not want to recognize such values. The job of criticism is, rather, to discover those traits to which the work owes its popularity. Such words, from a man who struggled for years to stamp out tawdriness in SF, are more than the admission of a personal defeat -- they are the diagnosis of a general condition. If even the perennial defender of artistic values has laid down his arms, what can lesser spirits hope to accomplish in this situation?

"Indeed, the possibility cannot be ruled out that Joseph Conrad's elevated description of literature as rendering "the highest kind of truth to the visible universe" may become an anachronism -- that the independence of literature from fashion and demand may vanish outside SF as well, and then whatever reaps immediate applause as a best-seller will be identified with what is most worthwhile. That would be a gloomy prospect. The culture of any period is a mixture of that which docilely caters to passing whims and fancies and that which transcends these things -- and may also pass judgment on them. Whatever defers to current tastes becomes an entertainment which achieves success immediately or not at all, for there is no such thing as a stage-magic exhibition or a football game which, unrecognized today, will become famous a hundred years from now. Literature is another matter: it is created by a process of natural selection of values, which takes place in society and which does not necessarily relegate works to obscurity if they are also entertainment, but which consigns them to oblivion if they are only entertainment. Why is this so? Much could be said about this. If the concept of the human being as an individual who desires of society and of the world something more than immediate satisfactions were abolished, then the difference between literature and entertainment would likewise disappear. But since we do not as yet identify the dexterity of a conjurer with the personal expression of a relationship to the world, we cannot measure literary values by numbers of books sold."

[1] - https://www.depauw.edu/sfs/backissues/5/lem5art.htm