Gnus has a brilliant system for assigning a score to postings in all sorts of clever ways. You have the simple stuff, like assigning a negative score to a given person, but you can also do more subtle stuff like scoring up postings that are responses to your own postings. It also has various forms of adaptive scoring.
The score then influenced the ordering of threads, highlighting threads that need your attention and hiding threads and postings that you do not want to see. (Most news readers had a bozo-filter that could do the latter, but which didn't really do any of the former well).
What made Gnus such a great newsreader was that, with the use of scoring, I could spend 10-15 minutes per day getting an overview of dozens of active discussions I was having across a bunch of newsgroups. At one point the total number of postings in the groups I was following was around 6000 postings per day, and it took me mere minutes to get an overview of what had happened that was of interest to me.
The idea of scoring applied to RSS feeds would have been brilliant. It would have made following a massive number of RSS feeds a far more attractive proposition.
I still think that there is an opportunity to revive RSS and make it relevant again, but I would recommend that people interested in RSS readers have a closer look at Gnus first. RSS readers need to do a lot more than just aggregate and display feeds. There are some great opportunities in figuring out how to add scoring in a way users can understand. Also I think that harnessing social to provide additional signals that can be used for scoring would be neat.
Is there an RSS reader today that does any of this?
Web forums, web mail, blogs, and web news sites were definitely a huge step backwards in terms of interface and features.
 - http://pan.rebelbase.com/
 - http://www.mutt.org/
 - http://www.claws-mail.org/
*: Winning means quite many very different things: for example you can win number of users / visits (ability to monetize) vs actual usefulness etc...
I get the feeling though that the issue with RSS was not altogether an issue of uptake or ux.. but more an issue of sites wanting to track their users. If RSS could allow for some sort of phone home (opt out / anonymisable of course) then maybe there might be more of a push from content creators.
Of course, this never really materialized. What we got was ... well, a mess. I think mainly because a lot of people tried to reinvent the wheel and did so badly.
I never saw RSS as something portals would be interested in. (And any time a site's business idea is to keep someone on their site for as long as possible, what you have is, in my opinion, a traditional, late 90s portal).
(Back in the early 00s I worked on web crawlers and to me RSS was interesting because it could have been used to aid us in finding fresh content. I talked to a few site owners back then about why they were so reluctant to add it and the sentiment was largely "we want people to find our content from our front page")
edit:  http://gwene.org/about.php
And, more importantly, it was so easy to follow a gigantic amount of threads and find the information that would likely be of interest to you.
Sure this required good readers and users willing to learn to use these but as a result it was incredibly more useful than what we have today. There were some people who simply geniuses and who were explaining things in great way: it was very easy to assign them good scores so that their interventions would stand out.
What do we have today? Inferior crap like StackOverflow because, supposedly, users would be too lazy to learn to use powerful functionalities.
I'm pretty sure one day we'll get some "Gnus meet StackOverflow" webapp which is going to rock our world. I can't wait for the next big thing because honestly we've made a gigantic step backward.
One of these days, those of us interested in a 21st century Usenet should really get together and make it happen. I never used Gnus (I was more of a trn guy) and I think Stack Overflow is pretty cool, but I do miss the ability to sift through large quantities of high-quality posts using the tools and interface that worked best for me.
The concept hasn't completely congealed in my mind, but some cool features would be: separation of content from interface, great APIs, pseudonymous identity with encryption and signatures, and some sort of a reputation system.
At the pace corporations "innovate", and considering their tendency to dumb-down interfaces instead of providing more advanced features, it might take another 10 or 20 years for them to get anywhere near the features Usenet news readers had 20 years ago.
I wouldn't hold my breath.