I think the forum need to show their existence on other social medias/forums to attract new people. Whether they run other social medias by themselves or working together with other projects like cointelegraph, coinmarketcap etc which Average Joe's read.
Yes, I agree with you. This is an important point to consider. Many people especially the younger generation, prefer social media activity much more than forums.
Another factor that may play a part in the lack of new users is the outdated style of the forum. The current format of the forum may not appeal to young people, who prefer modern, more engaging, and easier-to-use forums.