https://github.com/graphql/graphql-js/graphs/contributors?fr...
:) So by your logic, i could say:
"If this considered a real world javascript/node, it's no wonder there's not a lot of people using it." which is obviously wrong.
You are using the wrong metrics to judge the language popularity. Virtually every OSS project has only a handful of core contributors.
PS1: Note that i am not arguing PostgREST is a great example of real world haskell, it's not for me to say since i have bias :)
PS2: You are right that the source code is not commented and it could use a little of that but what you are missing (because you are not used to haskell) is that a lot of the documentation for haskell projects comes from the types and type signature of the functions. So just by looking at that, in a lot of cases, a haskell programmer can reliably tell what the function is doing without any documentation