I don't think that's right. Sure, the language runtime environment often uses a lower level language to speak with the underlying hardware or abstraction. But large parts of standard libraries may be written in the language itself. Build systems may have a little bit of shell scripting to get going, but larger such programs would often be written in the language itself. This certainly is the case with NPM, Yarn (JavaScript), Maven (Java), Gradle (multiple JVM languages), Rake (Ruby).