In my experience, LDS publishers and critics repeatedly ask "when will a mormon author produce an LDS masterpiece" meanwhile, back at the office they're nickel and diming those "run of the mill" mormon authors to death. Is if fair to ask when will LDS publishers begin treating LDS authors like professionals?
The flippant answer is: when LDS authors start submitting professional quality manuscripts and when LDS readers start demanding it.
As rude as that sounds, however, it is also the true answer.
There is a customer base that is demanding LDS literature. There are not enough quality LDS manuscripts being submitted to meet that demand. Publishers fill the gap with "run of the mill" books, which the customers accept. Publishers will increase the quality of their output when they have a greater selection of high quality manuscripts to choose from. No publisher ever says, "I think I'll publish this mediocre manuscript even though I have several really high quality ones here on my desk." They always pick the best from what they have.
It takes a lot more money and effort to take one of these "run of the mill" manuscripts and really polish it until it shines. Unfortunately, an increased investment of money and effort rarely pays off in significantly increased sales.
Let's say that if you spend $200 for editing, you can sell 2,000 books. Or you can spend $1,000 in editing, and sell 3,000 books. The investment just doesn't pay out. Publishers will start putting their money into editing when it becomes cost effective--for example, when that $1,000 corresponds to sales of 10,000 copies.
As long as the customers continue to buy mediocre books at acceptable levels, publishers will continue to accept mediocre manuscripts. And unfortunately, some publishers don't care as much about quality as they should. They crank out really bad books, slap a pretty cover on it so it will sell, and they don't care that it's embarrassingly sub par. Other publishers think they're putting out high quality product, and they're really not.
On the other hand, there are some publishers who are really committed to raising the bar for LDS fiction and fortunately, the industry as a whole is moving in that direction. It's just moving slower than some of us would like.