I graduated from college with a degree in English & Creative Writing, and wrote several stories for my college's literary magazine. Some were accepted and some were rejected. What I noticed after a short time was that everything I wrote that was about death, loss, oppression, and other negative topics was accepted and anything with a positive slant was rejected. I don't know about others, but I find a steady stream of downer stories boring and depressing. Since that was all they seemed to publish, I canceled my subscription.

As you mentioned, it seems that certain literary magazines are still doing relatively well. Maybe if more literary magazines published things that people wanted to read, they'd be better off.