I think what really put an end to RSS was sites like Digg.com (not sure if they were the first, but they're the first I remember), where people would submit stories and users would vote on whether they were good or not. Aggregators existed before, like Slashdot.org, but were curated by editors. Reddit.com and others followed, and RSS feeds became much and much less popular. I kinda view the result of the "social aggregators" as an RSS feed with the content ranked.
There's a disincentive to publishing an RSS feed, as the content creators would much rather you visit their home page so they can serve you some ads. And with people visiting their home page, they're more incentivized to keep the crap headlines to a tolerable level. Of course the downside of RSS not being mainstream anymore is that smaller/independent publishers that don't make money on clicks either don't know it exists, or don't think the effort is worthwhile.