but where do we draw the line to what kind of content is acceptable to write about?

We don't. That's the point. That's the entire point.

Any human experience - even the most painful and horrifying - can also be part of a story. If it something that can happen in real life, I see absolutely no valid reason why it cannot be written about. We can debate over how a specific piece of media is written and whether elements in it are actively harmful (think Hogwarts Legacy Blood Libel: the Game for one), we can choose whether to engage with it or not, we can boycott it - but drawing arbitrary lines on what subjects can or cannot be written about, full stop, is an all-around horrible idea.

"Oh we would only forbid the really wrong stuff, it's not like it would be censorship, just going to make things better for everyone" is not the innovative thought that a lot of people think it is. It has been applied, often with plenty of good intentions, throughout the entirety of human history. Everyone thinks that the line they would draw is the right one. And there has never been a single instance when this has not backfired horribly.