C#/.net is popular as an enterprise language for a number of different applications (not only web development). Its possible most of the companies hiring in your area don’t build web apps, and thus don’t focus on JS as their language.
JS/NodeJs does not work well in some use-cases, such as high CPU applications, as such its not a be all end all language. The same is true for almost any language and technology in one aspect or another. This doesn’t mean JS/NodeJs isn’t in demand, it just means it isn’t going to be in demand for all use-cases.
Finally even “ancient” languages are still around in some form or another. Languages like C, COBOL, and Visual Basic have been replaced by newer languages and technologies, but one can still find plenty of jobs for these languages and technologies.