They were all the go during the "Web 2.0" heyday but started to fade into obscurity in the mid-2010s. I did a bit of poking around and found the features to support them were removed from most browsers for a few years already. Back in the day I could check a whole bunch of news sites and blogs without having to open the front page of a single one of them. A great timesaver particularly if you are prone to doomscrolling as many people are these days.
There are browser addons to restore support but they're not widely used.
Have attached a screenshot for those who haven't ever seen it / don't know what I'm blathering on about.
A shame. I loved following blogs via RSS on Google Reader. Also, the Web has been ruined by cookie questions/popups/ads etc. Not the same web I loved back in the heyday of late'90s, early 2000's. Usenet was great too for forums. Now we have this debacle of a site :/
Strangely I just discovered that if you go to the AH main page it has a RSS feed. As do the other forums
It was an absolutely brilliant way to find and read interesting things on the internet. Wasn't suiting the advertising model that supports how humans interact online though, so was pretty much taken outside and shot. It's one of the principal reasons people are getting increasingly bored of text-based internet.