That's just parsing JSON and interpreting the data. Since parsing JSON and producing arbitrary object models is a solved problem, parsing an x-like format that uses JSON is also a solved problem for all x (developing the object model to use for it is an issue, perhaps, but you have to have that before you can have any serialization format, so that's not a distinguishing problem between different approaches.)

Note that I am not, here, endorsing JSON over other alternatives; the same is obviously true of XML, HTML, YAML, or lots of other potential formats.

Right, the only point I'm making is that ease of parsing JSON shouldn't count as a factor against RSS since RSS parsing is already more done than parsing any JSON-powered RSS alternative as the object model is already defined and implemented.