This tends to happen more with newer, inexperienced writers, but it also happens with those who have been hanging around writer circles long enough to understand the mysterious and baffling world of genre. Here's the basic scenario. A writer generates a manuscript that doesn't fit any particular genre. There's a mystery, but it's handled in a subplot. There's a romantic relationship, but it already exists on page one and doesn't really change by the end of the story. The main character is female, but her personal journey doesn't form the central plot or structure -- some other external plot does, and the protagonist doesn't change as a result of the external plot action. There are family dynamics involved, but those dynamics are not large enough to carry the weight of a family saga. There are supernatural characters or horror elements, but all the other competing elements relegate them to a supporting role. There might even be a political assassination attempt thrown in somewhere around the midpoint. And, the cherry on top, it's set in 1870 in Wyoming. In short, the book is about everything and nothing, and it doesn't fit into anything like a recognized genre, let alone a particular subgenre.
A book like this will be hard to market even during good times. During these times of across-the-board uncertainty, it will be virtually impossible.
I know that's a tough reality. Believe me, I see the evidence of how tough it is for writers with this kind of book. This is something I deal with pretty regularly with clients, and these dealings tend to follow predictable patterns. I suggest ways to shift the book more firmly into one or another genre (which is the right move, especially if you're a new writer with no track record or fan base). I usually outline more than one strategy to accomplish this so that the writer has a choice of direction. But the response is usually uncomfortable, sometimes even hostile. "Why do I have to change this?"
Because you do. Because books are a retail commodity marketed under "the same but different" principles. Because you are an unknown. Because until readers start asking bookstore clerks for your books by your name -- "Do you have the latest Steven King/Scott Turow/Nora Roberts?" -- they will be more likely to buy your book if it bears a resemblance to the latest King or Turow or Roberts.
Someday, you might have enough pull, or times might be good enough, so that you can publish your hybrid romance/mystery/horror/political thriller/family saga/coming of age/western novel. But when you're new and untested, the best way for you to find readers will be by writing to recognized genre standards. Innovate within the form now, and innovate the form itself later. (If ever. Chances are, after you have ten or so books out there, you'll also have a tidy collection of tales of woe from authors who risked books like that. Seriously, folks, there's a reason these books rarely get published. No matter what happens on the actual last page, the story almost never ends well.)
Does this mean the hybrid book is terrible? Of course not. In fact, I've read some excellent hybrids over the years. None of them have seen publication, but they were darned good, and I'm glad I had the chance to read them.And yes, there are tales of breakout, genre-busting books -- and yes, some of the books I've read could find huge crossover readership. Or they could end up disappointing readers who were looking for "the same, but different," and found not enough same, and too much different. Regardless, the reality is that these books are a damned hard sell, and if you're interested in being a career writer, it's wise to start by writing to genre specifications.