Also, marketing is expensive. You can spend $50 to place one copy. You'd honestly do better buying your own books, if you care about bestseller status, which will do less for you than you might think, but pays off in certain categories. [1] "Just do marketing" is advice every self-publisher hears, and yet most don't make money. Even most traditionally published authors, who benefit from enormous unfair advantages, fail.

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.