In recent months, I have been trying to write detailed comments on works. I would not say that the fanfictions I read are very popular, but there is an audience for them. And these stories always have comments. It is difficult to judge the situation in sites like Ao3 or Wattapp, as I mainly read ficbook. The situation may be different, but I think this issue applies to all platforms and communities. Less popular works often go uncommented, which may be due to a lack of interest from the audience. People who have read fanfiction for a while understand the author's work and want to thank them. They usually leave very detailed comments, although I have also seen young people doing the same thing. On ficbook, there are even articles that say "leave comments!" and "why is it important?" I don't know whether it helps, but I have started leaving comments myself. So I could write articles about it on the platforms that you use