I don't understand the article. He seems to be confusing using a language in a project vs using a language as the primary one in a project. We might say "Assembly language is not suitable for large OS kernels. Do not write your OS kernel in assembly language."

But I don't think that follows. Assembly language (the article's metaphor) is something that most OS kernels will use from time to time and in moderation. Similarly I don't see anything wrong with Javascript for some pieces of a large web app.