Forums are for discussions, social media platforms (FB, SnapChat, Twitter, etc) are for soundbites and that's the difference, the younger end of the market aren't up for lengthy topics and discussions, they are more than happy just posting short soundbites, lols, gifs and emoticons, to garner reactions.
If you want a forum platform to be able to compete with such you would need a method of being able to reply quickly to the comment the user is reading/looking at.
A 'write a reply box' at the end of the page will not do, the user will need to be able to 'comment' immediately below the post they're reading