As for email, to me it just doesn't serve the same purpose that IM does. It's analogous to sending letters back and forth as opposed to having a face-to-face conversation -- the increased time lag between replies encouraged by the medium has a huge influence on the nature of conversations that occur through it.
I still use email, for example when I want to send something more in-depth to someone and I don't expect a quick reply. But it's not the right tool if I want a real-time, informal conversation with someone, which is most of my conversations.
I have a group chat with 2/3 other friends I've know for 20+ years. Then I usually text others individually.
Facebook is an awful medium to conduct intimate conversations over. After two failed attempts to ditch it in the past, I've been off Facebook for a year. I can attest that you won't miss it. Just use SMS.
>That being said, I limit my facebook usage to messanger and wishing people happy birthday, so I guess it could be worse.
You don't need a platform, you need a messaging tool and, if you don't mind the lack of encryption, you could just use email.