I am a former publisher of several large forums using VBulletin and am a longtime forum user/ owner. I think most forum operators have seen an erosion of growth as casual users and general conversation migrate to newer social platforms like Facebook, Twitter, Instagram, etc.
In the old days of the web, we sought content. We explored, we surfed. Today, casual users have content delivered to them in a feed or wall. While this can be as complex as a tastemaker algorithm, I envision a simple feed whereby the user chooses forum categories to follow, or topic tags, or users and then has them delivered to in a feed specific to that user. Rather than looking at the latest overall threads as is also available here, or in the specific categories which takes time, a user instead gets a feed of just the things he or she chooses. I see this more like Twitter where I choose what or who to follow rather than like Facebook where they throttle things based on their perceptions of my interests or their own priorities.
Have you considered a wall style view for Discourse? Is anybody else interested in such a thing?