What was wrong with it? I mean there were problems with the twenty slightly different versions, or whatever, but they were solved by Atom. What do you want in open content syndication that wouldn't naturally build on Atom?
lack of rich media support kept RSS limited to text based reader applications and therefore a less appealing option vs. just bookmarking actual websites and reading them in a browser (or mobile browser).
dependence on aggregation tools running clientside also meant that operating an RSS reader had just as much overhead for the user as just using their browser already does. if its a worse experience than reading in the browser, and is equally complicated to do then there's no good reason to prefer RSS over a browser.
a replacement technology should, in my mind, not be something that competes with the browser experience (as RSS/Atom did). at this moment I don't think there's a compelling use case for a replacement at all which is why we're not actually seeing active development of one. what I expect will happen is that more and more websites will eventually implement RESTful API's and then we'll just have the option of syndicating over REST calls instead of relying on RSS.
What was wrong with it? I mean there were problems with the twenty slightly different versions, or whatever, but they were solved by Atom. What do you want in open content syndication that wouldn't naturally build on Atom?