What do you think of most of the so-called popular fiction nowadays, like the novels one can typically buy in the grocery store?"
My answer may surprise you.
It is sort of faux intellectual nowadays to claim that most popular fiction is "crap". Such claims are especially common among novelists whose books aren't sold in mass market outlets. (This is basically every author who isn't a household name, since there is a premium on shelf space at Walmart, etc.)
However, I'm not about to make that argument, simply because Blood Flats, The Maze, or Eleven Miles of Night aren't (yet) on the New York Times bestsellers list--or on the shelves at Walmart.
There are a few exceptions and disclaimers here, of course: I have to admit that I don't see much redeeming value in the Fifty Shades of Grey books. But then, I also have to admit that a.) I haven't read them, and b.) the Fifty Shades of Grey series was specifically targeted at a subset of the female market. Which doesn't include me.
Stephen King--probably the most widely recognized American writer--has called fellow bestselling author James Patterson an author of "dopey thrillers". Patterson's books are admittedly formulaic, and won't usually please the voracious, habitual reader. But that, you see, is the point: James Patterson writes simple (but highly accessible) novels for folks who only read three or four fiction books per year. Patterson writes not for me (I read at least a book per week) but for the person who picked up a novel in the airport bookstore, because he discovered that there would be no in-flight movie.
I've read most of the Dan Brown books--The Da Vinci Code, Angels and Demons, and, most recently, Inferno. These were neither the best nor the worst novels I've ever read. But again: Brown writes fast-paced novels that can be devoured by almost anyone, even those who don't ordinarily "like to read".
That said, there are quite a few popular novelists whom I do like. These include: John Grisham, Michael Connelly, John Sandford, Brad Thor, Clive Cussler, and Gillian Flynn.
These are all "Walmart authors"--in the sense that their books can be readily purchased at convenience marts and grocery stores. (I discovered John Sandford at Walgreens, incidentally.)
John Sandford and Michael Connelly are masters of police procedurals. John Grisham's novels repeat plot elements and themes, but Grisham changes each story just enough to keep the reader guessing--and most of his novels are page-turners. Gillian Flynn's work is dark but still somehow compelling--and compelling for a large number of readers. Brad Thor is the master of post-9/11 spy fiction (a distinction he shares with the late Vince Flynn.)
Cussler's novels are often unrealistic, and yes--some of the dialogue is cheezy. But they're great fun. And at the end of the day, fun is the name of the game where fiction is concerned.
So...yes, I do like so-called "popular fiction". Even at the mass market level, there are a lot of highly competent writers doing quality work. And while those authors are competitors, in a sense, they are also building potential audiences for every lesser known author--including yours truly. Fiction writing, alas, is not a zero-sum game.