Totally disagree with your viewpoint.
You seem to suggest these products are distinct. Clearly they are not. Facebook Groups have significant overlap with Discourse both functionally and in their mission.
If you are happy using Discourse in a silo and you are finding your instance successful that’s great.
As you may or may not have noticed from other posters, eg here and here, however, is that Facebook Groups have been observed to have been impacting the popularity of some Discourse forums.
I think one would be naive if one thought Zuckenberg and gang would not be delighted to have a forum fail and have all its users move to using Facebook resources.
Facebook is not just a ‘thing’ on its own, it’s a highly motivated, competitive and powerful business who would take away your community if you let them and hide them behind a Facebook login. They will gladly bend their product into more shapes if it means they can further dominate people’s attention.
I’m merely suggesting a way the ecosystem of Discourse might be extended to combat that.