The thing these and all other similar efforts miss is the importance of network effects. Everyone uses Slack because everyone uses Slack.
The real problem that needs to be tackled is one layer down: providing an open, distributed alternative for authentication, identity management, and data interchange that is secure and robust enough to provide a backplane for things like this and that is easy enough for anyone to use that it can be pushed out to the mass market. I can't stress the last point enough. It must be stupid simple easy to use or it will fail. It also must offer a good and simple developer experience (DX) or it will fail. DX is part of UX. Things like XMPP are nightmares for devs and sysadmins and fail badly here.
This is a huge missing piece of the web.