Paul, I like how you’re questioning what is going on with micro.blog and what it is. The toughest part about it is that it is being sold by many different people in many different ways and it’s something slightly different depending on who you are and what you’re coming to it with. It’s all a question of framing.
I might suggest that you’re framing in an odd way, particularly given what I think you’d ultimately like to see on the web which you mention in your closing paragraphs.
To put things somewhat in “Automattic” terms, micro.blog is almost just like WordPress.com in that it’s a hosted content management system with a somewhat both open and closed community attached to it. If you’ve got a WordPress.com account you can easily post replies and likes on other blogs within the WordPress.com ecosystem and WordPress.com also has a slick feed reader you can use to easily subscribe to content (and even more easily subscribe if you’re within that WordPres.com community).
Just like WordPress.com, micro.blog-based sites (if you’re using their CMS) provide you with a physical website that includes RSS feeds and most of the other typical website functionality, so in fact, if you’ve got a micro.blog-based site, you’re fully on the web. If you’d like you can take your domain, export your content and move to WordPress, Drupal, SquareSpace, or any other CMS out there.
The real difference between micro.blog and WordPress.com happens in that micro.blog sends webmentions to provide their commenting functionality (though their websites don’t receive webmentions in a standalone way technically and in fact they don’t even allow manual comments as micro.blog-based websites don’t have traditional commenting functionality (yet?).) Micro.blog also supports Micropub natively, so users can use many of the micropub apps for posting to their sites as well.
Now where things get a bit wonky is that the micro.blog feed reader will let you subscribe to other m.b. users (and recently ActivityPub accounts like those on Mastodon) which is why it feels like a Twitter or Facebook replacement. But the difference is that while it feels like you’re in yet-another-silo like Twitter or Facebook, over on the side, you’ve got a traditional free standing website!
Incidentally micro.blog also uses their feed reader as a side method for displaying the replies of others to your posts within the ecosystem. If you have a non-micro.blog website that feeds into the system (like you and I–and incidentally Brad too–do with WordPress) then micro.blog sends webmentions to those sites so that they don’t necessarily need to be “within the community” to interact with it.
In summation, I might suggest that while some people might be framing micro.blog as a replacement for Facebook or Twitter, the better framing is that micro.blog is really what you were hoping it might be. It is a traditional web host with its own custom content management system that supports web standards and newer technologies like Webmention, Micropub, WebSub, and pieces of Microsub. Or similarly and more succinctly, Micro.blog is a turnkey IndieWeb CMS that allows users to have a website without needing to manage anything on the back end.
Now that we’ve re-framed it to look like what you had hoped for, let’s see if we can talk Manton into open sourcing it all! Then Automattic might have some more competition. 😉