RSS's challenge has never been apps, it's support from publishers to keep using open formats.
A modern format would no doubt have to be JSON- or YAML-based and have its human-readable content in plain text or markdown, so it'd have to be pretty much readable with a plain text http client, like curl.
So, just let RSS die the slow death it's been going through for good reasons and bring something consistent and straight-forward into its place. Something that you could easily generate and parse from any modern language without specific libraries.
Bringing RSS back is like trying to bring SOAP as a RPC system back; it just won't fly anymore no matter how much hot air you try to pump into it. We know better now and have better ways to do the things.