First thing I want to say is that it is not necessary for fiction to be good for people’s mental health. Art for art’s sake has value, so does individual autonomy, and people can create and consume fiction based on what they want and what they value without having to make it medicinal so they can justify it as a social good.
Second thing I want to say is that it is not possible to create fiction that is universally good for people’s mental health. Tumblr fandom tends to treat certain mental health needs as implicitly the most legitimate, and inherent universal needs, but it’s way more complicated than that. Many people will absolutely thrive on stories of loving, supportive families, while some people will need to avoid them due to their specific family history. Some people are helped by reading about characters they enjoy practicing healthy communication and getting positive results, while other people might come away hearing, “Everyone can do healthy communication and get helpful responses if they try hard enough, so therefore the problem must be you screwing it up!” Some people might find “Destroy the evil abuser” revenge fantasies a helpful way to process anger, while other people might find they do more harm than good. A lot of people find stories of a character being gently nurtured by someone else, while some people have negative associations with other people trying to take care of them and have bad psychological reactions to these stories. (And let me tell you, if you have a bad associations with soft pastel nurturing that mean it can put you in a bad headspace, Tumblr can be pure hell.)
Mental health needs differ. They’re not always soft. They’re not always predictable based on a diagnosis, or a few details of someone’s history. They’re diverse, individual, and sometimes mesh poorly with stuff that most people would consider healthy and wholesome. Your story might be helpful for a specific person, or for a number of people, but there’s no such thing as the universally healthy story or the universally unhealthy story. It is literally not possible to write something for the general public and ensure it’s healthy for everyone who reads it.
