I'm hardly the one "blaming" writers for selling what's being bought. Then again, most of my writing hasn't been of the Ahtistic sort because I'd rather be rich than respected.
But the fact is that publishers are also mercenary -- which kinda makes sense when running a business rather than a public service agency. So, when they're itching to jump on a trend, they tell their readers (the ones chained to desks, not the ones with cash to spend) to flag everything that a half-blind ox might conceivably confuse with the Hot Topic.
Soon enough, that house's category is packed.
Now, if they've been picky -- & some lines are sharp that way -- they've discarded the poor fits, shaved some rough corners off the near-misses, & maybe even asked for a few quick rewrites.
Then again, there are lines that figure they're just peaches with "good enough," & all they gotta do is slap a title & some cover art on it, & the rubes'll pony up pronto. Look at all the "chick lit" titles that don't fit the early writing in the niche, yet the titles are in ribbony fonts, there's various paperdoll bodies (or body parts), & the whole thing's slathered in pastels that, if they exist in Nature, usually offer an opportunity to cull failed genetic lines.
When readers get burned, they damn the entire niche with memories of the latter, not the on-target former.
I've got a rant about mystery stories. In past decades, it's become very tough to find a writer who's good at writing mysteries that don't involve human death, particularly murder. Now, I've got nothing at all against a well-played croaking-off, but it strikes me as a lazy literary gimmick that offsets the need to actually write decently. The "fake cozies" seem to have a murder or three a week in a town of 800 people, & none of the residents thinks, "Hmm, maybe I oughta move to Haiti where my chances of survival are better."
In the past five years, we've now seen where every-other mystery story involves serial killers. If there were one-tenth the serial murderers in the Real World, we could finally set aside fears of overpopulation, because it's being taken care of. Again, solid writing is replaced with a sensationalist gimmick.
I simply don't think it'll "implode." It'll simply become so pedestrian that fewer professionals will toss it in to move a plot along, & they'll either start writing again or come up with some other bright&shiny object for the new Big Thing gimmick.
Plus ca change.
Of course, I had no say on the cover -- if it were up to me, I would have had a close up of a devil's pitchfork with a G-string dangling off one of the tines. 
Many thanks!
