I'm not going to pretend that my shelved book SACRED FIRE is flawless. However, the reason it didn't take off wasn't due to a flaw. Agents and betas all told me the same thing; the writing is strong, but the market isn't buying Ancient Rome.
On the one hand, it's totally unfair. You would think that every quality book should have the chance to be successful. If it's well written, people will read it, right?
On the other hand, I can't blame the market for not reading Ancient Rome. I don't read Ancient Rome either. Part of the reason I wrote Sacred Fire was that I wanted to do something from that time period that was fresh and original, something that focused on religion instead of war and politics. I've read books in that time period I really liked, but it's exhausting to read about a culture so different from our own, so I can only read so many of them.
I can't be mad at the market for not reading books I don't read, I can't be mad at editors for not publishing books that don't get read, and I can't be mad at agents for not taking on books that don't interest editors.
(Of course, if there were more Ancient Roman books I like such as Stephanie Dray and Kate Quinn, I'd probably read that time period more. Now we're getting into a chicken-or-the-egg argument.)
A friend of mine had to shelve a book that I thought was fantastic for the same reason; it was Dystopian, and people have lost interest in dystopian stories. She was able to get her next book published because it was sci-fi.
At first I was irritated that people have lost interest in such a fascinating genre so quickly. Then I realized, I've lost interest too. I took a Utopian/Dystopian literature class in college, I read Hunger Games, and I read Matched. I might read Divergent because everyone says it's great, but for the most part, I'm not likely to pick up another Dystopian book unless it's extremely original and popular.
To sum up, it certainly sucks for writers that they need to keep up with a mass of ever-changing tastes. It takes years to write and publish a novel and much less time for a fad to go out of style. Shouldn't art speak for itself? Shouldn't quality be the only thing that matters? Isn't it cruel to turn your nose up at a good book?
But you can't force readers to buy something they don't want to read, and I can't be mad at readers for not buying something I probably wouldn't read either.
It is what it is.