Thanks for the link. It's interesting, and I hope you find a way forward with that, it would undoubtedly be a useful addition to the ecosystem.
But my gut feeling is that there's not enough interest in RSS right now to drive widespread adoption of a new version of the spec. My approach would be to focus on improved UX over existing feeds, rather than speculatively expanding the spec to make feeds richer.
The main advantage of my approach, I think, is that it adapts to the individual end user's needs. If all my subscribed feeds are tech-focused and I use a generic published taxonomy, I'm going to end up with 60% of my items in "Technology" and 30% in "Computing". If I use a chatbot to dynamically bucket stuff, I'll get "Micro PCs", "Graph theory", "Golang", etc etc.