What is that? Facebook fills a niche that nothing else tries to. Facebook also does lots of other things that others do better, but they have a niche in sharing the semi private lives of friends with each other that nothing else does.

Semi private life sharing can be done in a discord 'house'. There are many other platforms that fill that same niche.

which involves everyone being on discord. Of all the social network platforms I've used/use, discord is the most stratified in terms of people/groups just not using it at all and having no interest in it.

Facebook initially had a wide appeal, discord never did.