I looked at Forem when it was announced, and some of the claims are the same claims that Discourse and Flarum have made; cutting edge, best of the best, does everything better than everyone else... Until it comes to functionality.
I did a brief rundown of the checklist I've used for when I do projects where accessibility is a priority, and used JAWS and a few other tools and applications to check problem areas. I also have had my step dad who is fully blind, deaf but with cochlear implants, and also has a neurological disorder that has slowly degraded his fine motor abilities, and feeling in his hands. From my rundown, I found that it is not any more accessible in reality to XenForo, or really any other platform. From my stepfathers test, he found it to be frustrating, but he is also use to a custom accessible install of XF myself and a developer who has since left XenForo behind worked on.
If you are wanting more social aspects added to XenForo, work with a developer to add more social aspects, or make suggestions for exactly what you think would work to the XF devs. I know when I have some free time I am going to work on overhauling the profile page to make it more content forward, and (sadly) closer to how a Facebook profile would be, but that is because the site I run has a lot of different aspects and elements that need to be tied in at a member level for future plans we have.