I honestly believe the only way forward for forums... is live threads. The person who wrote their piece, can then see that someone is live responding to them, and thus they know they have a response coming soon, and will feel far more engaged to communicate via forums IMHO.
For the mobile world we're turning into, no... it doesn't. XF is made to add-on to... and even standard XF isn't close to optimal for the mobile web.
XF needs to have an output system that combines ALL JS and CSS into a single file AND that system needs to incorporate ALL additional styles and add-ons a user adds. It needs to be compressed, minified, and output as a single file. People get all jumpy about this... they say it can't be done, causes issues, blah blah blah... but it can be done, is being done (especially in wordpress) and works flawlessly. Options for control of how this works is the key. When a single piece of JS doesn't play nice, then you want to be able to singularly pull that and load it by itself OR input it direct into the page (depending on size) for inline loading where it can be minified and compressed with the page.
Lazy loading needs to be default in XF. A mobile page doesn't need to be waiting for images not seen for 5 minutes of reading, to be awaiting loading just to start the page.
On images... images need to be compressed and scaled automatically to suit key system settings, so if someone uploads a mobile phone full size picture, it scales it, compresses it, and loads the optimal viewing size image only dependent upon device type used. Mobiles should only be downloading a scaled version of an image for the devices capability... not a CSS scaled version, which still means downloading far more data into a page than need be.
Yes, XF is good, BUT, since its inception the world has gone more mobile every year. Stats are progressively shifting each year to more mobile than desktop viewing. The best we have for mobile viewing is wi-fi, but the standard is 4G, and that means everything needs to be optimal for mobile downloading and viewing.
This is the way things are now, this is absolutely how any site who wants to compete for market share in the next few years needs to be. If you can't do it from a desktop style, the system needs to cater automatic mobile detection where a pure mobile style is delivered, where everything is automatically scaled and literally removed, so the minimal features are delivered for maximum performance to mobile users.
On average, any page that takes over 2 seconds to load, you lose 10% of your user audience just due to slow loading content.
Software performance is everything now, and only becoming more fundamental. IMHO, wordpress is leading the way in this area, along with some key developers. Acknowledged, this is not WP, nor does it have its development following... but if one is rebuilding the software from the ground up already, these are essential to success today.
Joomla took a huge dive due to its outdated, slow, underlying foundation of code and lack of performance. They shifted primarily to wordpress... and newcomers like Ghost have a steady influx due to meeting and ticking all these performance boxes for simplicity and speed, out of the box.