I wrote about this recently[1]. The "problem" with RSS, that essentially lead to it falling out of favour, is that it is pure consumption, not interaction. You can't "like" an update that comes to you via RSS, nor comment, nor easily share. It's difficult for sites to monetise it, or track, or promote their own agenda. It's not "social" and since every other site these days needs to be social, whether through aforementioned ways, or adding some sort of messaging process, it's not a way that sites can keep users hooked on the site to boost ad impressions.
RSS is pure content, curated only by the consumer and presented in chronological order not algorithmically messed with, which is why there's nothing better.