Discord is 100% social media. Just like WhatsApp. MSN definitely was, remember MSN Groups? MSN Chat (the IRC knock off), and a bunch of other things. As someone who has consumed social media and chat platforms, I will note that most chat platforms are social media in their own regard. Habbo Hotel is another example of social media. :)
Sorry but I don't consider WhatsApp to be in the social media category since it's just a chat app for your contacts, not an A/B algorithmically driven carousel of media to keep you hooked in and for strangers to hit you up (unless they have your phone number). However I do think Meta will try to slowly make it a social media app.
It's not just for your contacts though, in other countries WhatsApp is used like Facebook pages for your local town too. There's all sorts of group chats on WhatsApp.
Kids in 5th grade use WhatsApp for entertainment to send hundreds of messages per day filled with memes and slop. From the perspective of one kid in a class chat, this is indistinguishable from an algorithmically curated feed.
> this is indistinguishable from an algorithmically curated feed
If a classmate is sending you slop memes, then it's human curated content from an acquaintance, and not algorithmically driven, unless you consider your friends bots.
Is it? If kids grab the top result of a massively A/B tested algorithmic feed trying hook people and/or maximize the controversy / engagement, then arbitrage it onto another simpler less gamified platform... is that really human curated? There's some truth to the idea that, as long as there is any social media, everything is social media.