There are a number of Facebook-related topics around here, and I’ve contributed to at least one other. But I think this is an important one to follow-up on too.
Restating and Clarifying the Problem
In general I see Facebook as a substandard platform that does many different things. So when we talk about it as a single thing, it’s not entirely inaccurate, but I do think it defocuses - if not confuses - the conversation. Some of what Facebook does, Discourse does not do and in my view probably should not try to do (the concept of “friends”, “pages”, etc. seem out of scope to me). But some Facebook functionality is actually very much aiming at similar basic goals as Discourse, it just does them poorly. I am speaking primarily about Groups here.
The problem is that Facebook makes it easy for everyone, at least at first. Easy as a user to join a group, to keep up to date on it in the feed of posts that they already visit, and easy to contribute with comments or new posts. It’s a familiar UI, notifications are centralized, and there is even somewhat “smart” filtering so that, for example, the group(s) I am a member of that have literally 1000s of posts a day do not completely overwhelm my main Facebook feed.
And it’s easy for Admins/Community Builders, too. Starting a group is free and takes only a few minutes, and you have an existing somewhat “captive” audience there (any of your existing Facebook friends, for one thing), who all have just a few clicks to make to join your community (as few as 1, “Join”, if you don’t want to require people to review rules).
Some of these Facebook advantages, especially for admins, are difficult to overcome, or are outside the scope of what Discourse as a product and team probably want to provide (e.g. free hosting for everyone). But we can and I think should try to tackle the user side of things, because without that built-in audience, fewer admins would choose Facebook Groups in the first place.
So we all agree that Discourse is better than Facebook Groups. And yet… there are many very successful and active Groups. This is a problem we as Discourse users, admins, community builders, and indeed the development team itself should all be thinking about seriously. Because those people on Facebook aren’t there because they think it’s the absolute best way to talk about their topics of interest or have good, er, discourse. They’re largely there because it’s convenient, in numerous ways people have talked about above.
So forget the “friends” concept, forget “Facebook is about people focused vs. topic focused”. That’s only true about some parts of Facebook. In Groups the post topic is the focus, not the person. Just. Like. Discourse. And that makes it a Discourse competitor. A crappy one, but one with an unfair advantage. I hope we can work to dismantle that advantage over time.
Possible Solutions
So what can we do? Well, most of the likely better (or at least most obvious) possible solutions have been raised in this topic already. Figure out a way to unify authentication (on an opt-in basis) and provide options to both admins and users to control that (e.g. for users “auto-login to Discourse instances that are part of Federated Discourse”). Determine one or more good methods for unifying notifications across multiple Discourse instances, and make it something that is cross-platform, including Desktop. Perhaps even create a unified “Facebook feed-like” view that presents Topics from multiple forums in a single list, ideally with topic previews. These are really the minimum we can and should be talking and thinking about, and hopefully working on, to overcome the Facebook inertia.
But maybe we can even get more radical. Personally, I’m looking into the possibility of actually injecting Discourse posts into the Facebook feed. Not by posting them to Facebook with e.g. Integromat, but by actually hacking the Facebook feed with a browser plugin. 
And if it’s possible to actually do (still investigating, and I know it probably sounds crazy), I am willing to put some money down on it. So I’m just saying, my money is where my my mouth is. If I can do anything to support efforts more focused on Discourse improvements like the above, I’m happy to do that too.
Edit: Sorry @RickThrivingNow , didn’t actually mean to reply directly to your post.