It's interesting to look back at the last decade and how things have changed. I think it's fair to say that discussion forums in general are mainly older boards that have survived to this day, rather than new ones that are sprouting up. Here it seems that the next generation is content with just setting up a social media group and cannot be bothered with developing their own site and community.
In terms of software I don't think there is that much of a difference in terms of the user experience between various forum platforms from a typical, old school forum user's POV. It's only the young generation that needs everything linked to social media and the huge emphasis on making the experience mobile-friendly that sets software solutions apart.
Otherwise I think a simple design/layout update to make everything more sleek and up-to-date could easily do the job. It's more about refining the existing experience and stereamling current features rather than revolutionising anything...
