Currently MediaWiki:*.json pages use nested tables to display the JSON data.
Nested tables are generally evil - low accessibility, longer code, longer render time, bigger RAM consumption, more difficult DOM/XPath/CSS selector addressing etc. etc...
Use more reasonable representation, for instance something like (my favourite) jQuery Based Pretty Collapsible JSON Tree Viewer (demo). It's an idea how it should look, the script itself would need to be modified, since we need the page to display the JSON data even without JS (like static <ul> in this particular example).
Developer notes
Test URL: https://meta.wikimedia.org/w/index.php?title=Schema:NavigationTiming&oldid=21012083&