No amount of marketing can help you out is your entire market is shrinking daily. Shriking markets are also not won by quality. The more competition, the more marketing then becomes the main thing, and you also need to alter the book in the process so that it fits the bite-sized pills you can push on most channels, or worse change it so much for the audience until it becomes something else entirely.
The worsening health of the market is a real issue. And yes, writing to market is a grind. Writing for virality is worse, because you compromise the work and also don't get anything for it most of the time.
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[1] Own-buys are common with business books. You take a loss, but you get a promotion or you earn speaking fees from the status of being a bestseller, even if no one read the damn thing. For literature, they'll cost you more than they're worth—you'll get a better advance, but not as much as you paid for the bestseller distinction.