I find JSON tedious and error-prone to generate by hand. I also frequently wish I could document the data with comments.
Others have written about these same ideas, e.g. [1]; after feeling the frustration for over a year, I decided it might be productive to actually build a JS parser to get the conversation started.
My main use cases are Node/npm package.json files, and test case data.
I whole-heartedly agree with you on the tediousness, but JSON has this dubious double-nature that it is sometimes written by hand but mostly used as a protocol. As a protocol we want (and I would even argue need) this strictness since it makes day-to-day operations easier and parsers generally more reliable (how many times have we seen someone implement their own JSON parser? Now, what about XML? The first is a nice evening the latter is, well, not...).
As for package.json, I would argue the problem is their choice of serialisation rather than with JSON itself. Right tool for the wrong job. YAML would probably be a better pick.
Why do you need to generate it by hand? Create object structures in whatever language you are working in and then simply serialize them to JSON.