If the writer was smart he'd write something EVERYBODY could understand.
Although I don't write at an advanced level (like only Ph.Ds can read it) I don't think a child should or could read my writing. (Child= someone with vocabulary and reading skills less than an eighth grader). I don't write for everyone, I write for AN audience, one of many. To illustrate, although Harry Potter might be easily readable, and "good" I have never knuckled under to read it. I opened one book in the bookstore, and felt the irresistible notion to pitch it across the room. I am sure that there is an audience for literary fiction. I've read a few literary stories and books and don't consider them all unintelligible.
I think there are various reading levels, that is why there are divisions for YA in the library and book store, but to write adult (non YA) books at a YA level is only doing the reader a disservice. I think when a person reaches 17 or 18 they should be reading fully advanced adult level literature (or books). Why? Because there is no incentive to read at an adult level if all an adult (18 is an adult) needs to do is go to YA. Next thing you know college textbooks will need to be written at YA level because these readers have never read at an adult level. This is not all blowing smoke. The ability to read is going down hill and I do think that YA and "dumbing down" is partially to blame.
Some people who write popular books obviously chose to write for an audience that has less than high-school reading skills. Some readers are impatient with what can be considered the "dumbing-down" of the vocabulary used in books in order to lure a larger audience into buying the book.
I also don't think that "experimental" writing is useless and elitist, remembering that the beat writers of the 50s were once experimental, and literary, earlier, writers like Hemingway were more experimental, Sci-fi writers of inner space in the 60's were "experimental" and could be considered "literary" in some cases (Harlen Ellison).
In fact, although reading experimental writing is sometimes not easy, you end up learning new techniques from it. Writing stands still for a while, but then, when it moves, it moves in the direction of the "experimental" literary style.
oh well, Just a few observations from the dark side.