Facebook? Twitter? Useless for these purposes.
I too remember E-Groups, as well as ListServ and MajorDomo. It truly saddens me that email lists have been all but replaced by Facebook pages, WhatsApp, and forums.
For every task there is a tool that will perform best, and for many things an email list or reflector is that thing. If you belong to a group of 500 like-minded individuals it's the only sensible route. There's no need for each member to maintain a list of members on their own system, and people are free to leave with no worry that the list emails will keep coming to them.
Email is the lowest common denominator - everyone has an email address, and can send and receive messages no matter how old or oddball their computing device might be. It's a shame that email has been devalued to the point where some people actually think that a Facebook group is a realistic alternative. Did I mention that an email list also doesn't filter messages based on some California kid's algorithm? And doesn't stick advertisements into the message? And can even allow attachments? That you can easily move from a group discussion to a private one?
I use forums for solving technical problems, and the fairly permanent nature of them works well for that. And I use Twitter for another set of tasks that are perfect for that medium. As good as those are for some jobs, there are still places where an email list is the easiest, most secure, and most flexible option.
Ultimately though what this demonstrates yet again is that we all need to take on the task of moving our work away from the Googles and Yahoos of the world and into our own hosted spaces. You simply can't trust that any of these corporations will maintain the services that you use, much less any archives that you may have created. Fortunately a lot of hosting providers have some kind of one-click install for email lists so a lot of the headaches are eliminated.