If we're going to talk about replacing XML with better data formats, why not switch to S-expressions?

    (feed
     (version https://jsonfeed.org/version/1)
     (title "My Example Feed")
     (home-page-url https://example.org)
     (feed-url https://example.org/feed.json)
     (items
      (item (id 2)
            (content-text "This is a second item.")
            (url https://example.org/second-item))
      (item (id 1)
            (content-html "Hello, world!")
            (url https://example.org/initial-post))))

This looks much nicer IMHO than their first example:

    {
        "version": "https://jsonfeed.org/version/1",
        "title": "My Example Feed",
        "home_page_url": "https://example.org/",
        "feed_url": "https://example.org/feed.json",
        "items": [
            {
                "id": "2",
                "content_text": "This is a second item.",
                "url": "https://example.org/second-item"
            },
            {
                "id": "1",
                "content_html": "Hello, world!",
                "url": "https://example.org/initial-post"
            }
        ]
    }