I'm the target audience for this app, but I don't really want to generate my own stories; I want to read. Generating stories is just additional work for me, and I don't know how good the story is before I generate and read it. If I had access to a library of human-reviewed stories, I'd just read those, knowing that they are at least okay. You wouldn't even have to review them yourself; you could have a system for users to rate stories.
You're selling this as an AI product, but I don't care about AI. I care about learning a new language by reading stories.