"Instead of blogging, people are posting to Tumblr, tweeting, pinning things to their board, posting to Reddit, Snapchatting, updating Facebook statuses, Instagramming, and publishing on Medium…"
From my perspective, what was really interesting and novel about the "blogosphere(s)" was the dimension that I'll call textual collaboration.
The ideal of the blog resonates with ideals like "civic engagement," "the public sphere," and other such somewhat high-minded stuff—in a way that seems rather neutered by those other media.
From that list, Medium and reddit seem closest. But when I use Medium, I feel like what I am doing is providing free content to a startup. I don't feel like I am just sharing text with friends and strangers.
On reddit, I do often feel like I am simply sharing words with others in a collaborative and open way, because there is less of a focus on the author as an individual "brand;" there are fewer swanky photos of Moleskines and espressos; there is more vivid discussion and real conversation.
Blogging, I think, was (and to some degree is) a balance act between public and private. Also a balance between publishing and drafting. A balance between permanence and ephemerality. A balance between monologue and dialogue. And so on.
From my perspective, given that I focus on "textual collaboration," it's quite interesting to look at, e.g., GitHub. Yes, people are mostly working on code together, but it's done in an interesting and quite fresh way.
Wikis, too. That never really took off, did it? Could it?