I think RSS is a vastly underused technology/tool. I wonder at what point people lost hope in it and abandoned. Not to say, it's completely abandoned, but it's not used as much as it should be used.
I personally feel like and I remember very distinctly that RSS (and Atom Feeds to boot) seemingly hit their peak with google reader and when google reader was discontinued RSS seemed to wane quickly thereafter. I’d be very interested in knowing if hard statistics back this up or not but my anecdotal experience suggests that this is indeed the case