JSON is fantastic for organizing and passing data around, storing it, even for configuration files where the user doesn't need to edit the raw configuration. If you are like me and write a lot of tools that run in the background, lack a UI and where the only thing a user will be doing is editing a configuration file and running it, you're asking for trouble with JSON. Curly brackets and nesting and lack of basic formatting are bad for UX, and while it's a fantastic compromise for machine and human readability, it focuses more on machine readability and the human readability is just enough for you to look at it. It is not easy for a human to parse with their eyes.
I go with TOML for my configuration files most of the time. I am not a fan of YAML or XML. I don't think those offer any real benefit over JSON, and both have more downsides than JSON. TOML is a breeze to read and understand just looking at it, and is analogous to JSON as far as machine readability to the point that it's trivial to convert to it when you need to.
I do use JSON a lot, even for configuration files, but only when I'm storing a configuration in a flat file that the user should never have to see.