[WorldMaker]

Joke: RSS Completionism is easy when there are so many fewer websites with good RSS feeds these days.

More seriously, a big shift in some of the modern RSS clients is feeding that completionism in tunable ways. I know Newsblur the best because that's what I've used for a number of years now, and it's got a number of tools like the ability to demote/mute certain tags or authors from given feeds or promote other tags or others to a "Focused" feed. It has a concept of "infrequently updated feeds" to bubble up those quiet but powerful feeds you might follow that you want to read first before diving into the river of whatever firehose feeds you also like to subscribe.

Some of the other modern RSS readers have their own similar tools.

The nice thing about RSS is that completion is still possible. All of the newer social media want to give you an illusion of infinite feeds that go on forever to keep you locked inside and "engaged". But RSS doesn't work on "engagement" and there's a natural end of new content each day.