Dave, I’m active on quite a few forums for different topics and have noticed that there tends to be a lifecycle, and some manage that transition well while others fail.
For a forum to thrive, it needs to have activity, which drives users to come back and engage. If there aren’t any new topics or discussions, traffic starts waning and users leave.
A common mistake is to have too many specialized sub-forums, which lead to postings sporadically specifically related to that sub-topic. Again, vicious cycle which reduces activity. The most active forums tend to have just a main discussion area, with perhaps one or two specialized sub-forum for topics that might clutter the main forum (for Axis & Allies, this might be TripleA and variants discussion sub forums). However, everything else could be in one main forum, with perhaps a tag to identify which game(s) you are discussing.
I’m just trying to drive traffic and spark interest again in this forum.