Looking at the list, what actually jumps out at me is there is probably a gap in the world of standards for a JSON-based replacement to RSS. Looking it up someone came up with the idea of https://www.jsonfeed.org/ and hopefully it gains traction.

In hindsight, it is hard to imagine a JSON-based RSS-style standard struggling to catch. The first project every aspiring JS developer would be doing is how to add a feed to their website.