We are trying to make up for the missing features in Plone 5, by cobbling together several other products, with Plone as the center of the user experience, and SSO integrating the user access.
With NodeBB as our forum server, Kaltura CE as our video server, Gluu as our user management server (LDAP), and Plone as the primary interface for the community users.
So, an example is a user on the Plone 5 site. Goes to a page with an announcement about a new video, with some information about the video. The video is hosted on our video server (Kaltura), and embedded in the Plone page (currently works). Users wishing to comment, see a forum/comment thread grabbed from the nodeBB server (while remaining on this Plone content page). If there are already comments, then they will see those in the forum/thread fashion below the video on that Plone page. They can click on the comment button, and add their comments, without leaving the Plone content page. When they finish their comment, the Plone content page refreshes (with any other new comments from the nodeBB forum page) , the Plone Content page now shows their own comment posted. ALl without leaving the Plone page.
This would be even better if we could integrate with a Collections page, so can be autocreated more dynamically, but that is a secondary step.