Google Reader. It actually let me add feeds, read them, and mark them read reliably. Everything after is focused on value-add instead of just fucking working.
It's a beautiful little app. Great native app on iOS, too.
tt-rss: https://tt-rss.org/gitlab/fox/tt-rss/wikis/home ttrss-reader: https://play.google.com/store/apps/details?id=org.ttrssreade...
It came out as a response to the closure of Reader, and I actually prefer it. They've kept everything very simple.