Did not know about MAM, but that sounds great. I also hosted a Mumble server for my friends for over 5 years, but it was basically never used because there existed a one-stop solution (Discord) that allowed for more stuff^TM^. TIL Jitsi was powered by XMPP, thanks. I personally have no problem with fragmenting functionality between different specialized applications, but it will always be a tough sell for those I know because they believe they can have it all in their cool app.
At the end of the day, communication services usefulness are upwards limited by the people you can reach through them. The need for everything to be easy and centralized for the user (ironic with respect to server federation, I know) is what has made me so hopeful for the Matrix protocol, since it is designed for allowing this while still being decentralized at its core.