Would J. K. Rowling have written seven Harry Potters if the first hadn’t sold so well? Would Knausgaard have written six volumes of My Struggle, if the first had not been infinitely more successful (in Norway) than his previous novels? Sales influence both reader and writer—certainly far more than the critics do. In general I see nothing “wrong” with this blurring of lines between literary and genre fiction. In the end it’s rather exciting to have to figure out what is really on offer when a novel wins the Pulitzer, rather than taking it for granted that we are talking about literary achievement. But it does alert us to the fact that as any consensus on aesthetics breaks down, bestsellerdom is rapidly becoming the only measure of achievement that is undeniable.
I've talked before about how we tend to get our cues for enjoyment from our peers and our surroundings. If we know everyone is watching a given show, we watch it too, because that gives us all something to talk about, instead of everyone else talking about Orange is the New Black and then me (unsuccessfully) trying to explain the appeal of Berserk.
Sales works the same way. Fifty million Elvis fans can't be wrong, and neither can millions of people throwing down bundles of cash to read 50 Shades of Gray or the latest bale from the James Patterson hay factory. Even if the books themselves are forgettable tripe, people still feel as if they've had some kind of experience worth talking about, and so they're not wasted. But that means the book itself is no longer the important thing; it's just a poker chip being passed between hands. The real subject there is how we feel like we belong to something and how we fit ourselves into a given group.
This isn't confined to best-sellers, either. Elsewhere in the article, there's this note: "... while in the past one might have grumbled that some novels were successful only because they had been extravagantly hyped by the press, now one discovers the opposite phenomenon. Books are being spoken of as extraordinarily successful in denial of the fact that they are not." (Emphasis mine.) Meaning that people talking with their peers about a given literary darling will use the word "success" as a signal between them: This book validates our tastes, and by the same token, us.
I think we need to examine closely the way social validation works, especially in environments where it centers around something that only looks like it's benefiting from such a boost. It's great that you can have something zoom out of complete obscurity and get into millions of hands, but if it comes at the cost of having almost no one see the thing for what it really is — and to make it all the more difficult for present or future folks to do the same — was it worth it?