I was at a con quite a few years ago. I still didn’t have a book published. I still didn’t have a pro short story published. I was an infant.
I went to a writing seminar/panel and one of the people on it was a tie-in writer who is now deceased. I’m not going to name him, because it’s really not relevant.
He gave me the worst piece of writing advice I have ever received. I was talking about the book I was writing (it happened to be Daughter of Fire).
He asked me if it had a romance.
I said no.
He told me that it was impossible to sell a book unless it had a consummated romance involving the main character.
I managed not to laugh until I was out of earshot, but I started right away mentally listing successful books that lacked that particular feature. Starship Troopers, all the Heinlein juveniles, 2001, etc. Furthermore I already knew some people were actively looking for books without romance.
But this was dropped on me as wisdom from on high.
Every single rule of writing is a guideline. N.K. Jemisin can write in second person (although it still doesn’t always manage to satisfy me; I’m highly averse to second). Some books need a prologue.
And when it comes to content? Don’t listen to anyone. Write your heart. Because if you do you’ll have people telling you your main character “needs” to be white.
You’ll hear the most ridiculous things, when the fact is that somebody out there is desperately craving the rule-breaking thing you’re writing.
The real challenge is finding that audience.
But then, it always is.