It sounds simple on the surface. You copy a link on a site into a feed reader app. Then whenever that site updates you get a nice readable article on the app.
But that sounds like something that could be accomplished locally. Why does every RSS reader I run into require an account or otherwise rely on the cloud?
The rent seekers push web services because they don’t think they can sell you a client app.
There are many nice completely free privacy respecting client apps for RSS on F-Droid.