He said that in the very next paragraph. FTA...
"But I think Twitter is fundamentally broken in certain regards. You get a lot of mediocre stuff along with that. Everyone thinks they’re interesting. [snip] So I’m not sure that there is a clear heir apparent. There's power in what reddit does, and what Hacker News does and to a lesser extent what sites like Slashdot still do. But the power has shifted to individuals."