Quality and community. I’ve been reading through the other responses and agree good quality is important. You’re not going to pay for poor writing. However for me community is up there and even equal to quality. I have unsubscribed from people who never respond in the comments, who never build a sense of togetherness or who have community that seems disparate. If I wanted just quality I’d buy a book or listen to a podcast. I come to substack for the connection and exchange. That’s what makes it unique.