RSS was a social network for blogs. It was a way to self-publish a feed which users could follow. It was decentralized. It competed directly with Twitter and Facebook.
RSS had a hard time. It was a fairly simple design, but the protocol took a lot of coordinated work to use. You had to get bloggers to generate the feed files. You had to get browsers to detect RSS availability and give relevant UI controls. You had to train users to know what RSS was. And on and on.
RSS had high overhead and a subpar UX. It was beaten by better products created at Twitter and Facebook. Google didn't see an opportunity to capitalize on their RSS app -- the most popular reader at the time -- and shut it down. (The Google Reader shutdown was especially sad when you consider their followup attempt with Google Plus. You should've appreciated what you had, Google!)
RSS was a good idea with a bad execution. It turned self-hosted blogs into a social network - that's cool. People liked the freedom. They liked having control over their blogs' aesthetic, and code, and data. But, RSS was too limited and too much of a chore to deal with.
The dweb is a way to publish and syncronize websites without using servers. You use browser UIs and Web APIs to publish sites. You can read and write site files. You can write websites that write websites. You can also live-watch files for updates. It's a global site publishing system that's realtime. We now have a dweb Twitter clone which has likes and reply threads. It's all done with clientside javascript. There's no server at all.
The dweb has the features of RSS for free. Devs don't think about the network when the build apps. They just think about reading and writing json files. The RSS qualities came along for free because the dweb is a giant networked realtime filesystem.
The dweb makes networking websites easy. Six months ago, a hacker named Devine wanted to make his own social feed app on the dweb. So what he did was, he wrote a tool that would generate a website for you. And this website had a feed and a publish box, and when you published, you wrote the post to a json file. Then your followers would see the update, they'd pull down the new post, and it'd show up in the feed of their personal website. This is all with clientside javascript. And it supported replies and threads.
The killer app of the dweb is networked personal websites. Dwebsites can sync with each other. They don't need a server. The web is their database. The owner of a website can do whatever they want there. That site is their space. They control the code and the aesthetic and the data. When you give people that much power and ownership of their own spaces, but network them like Twitter and Facebook and have the same level of convenience, you get a user-driven & user-owned social network. That's a killer app.