Earlier quoted context omitted.
I'd say that simplest "production-ready" criterion is this: does it have an officially supported and stable release of a IntelliJ IDE (there is a slight Java-ecosystem bias, but I think it's only slight). So the mainstream languages are...: C/C++, C#, F#, Go, Groovy, Java, JavaScript, TypeScript, Kotlin, Objective-C, PHP, Python, Ruby, Scala, SQL, Swift, VB.NET (source: https://www.jetbrains.com/products.html ). Soun…
So, from the top of my head, Erlang, Haskell, OCaml, Perl, Fortran, Cobol and any type of shell script is not production-ready. Nice to have that clarified. :P
I wish that I knew a phrase to mean "has all of the documentation, tools, and libraries that are needed for an average team of developers following common practices to be likely to successfully ship and effectively maintain commercial projects, consistently".
Many really interesting languages and frameworks don't pass this criteria. It doesn't mean that they are a failure: the idea of programming languages that are designed for teaching or research, and are specifically not for commercial use, perhaps used to be more common than it is now.