[klibertp]

> the skills of software engineers are tied to the particular language or framework they are using

Well, not all of them of course, but yes, knowledge of a particular language matters.

For example:

a) idiomatic code in a given language is easier to maintain, a programmer who doesn't know this language won't write idiomatic code for awhile

b) lack of knowledge of available libraries may result in reinventing them poorly, leading to NIH syndrome, which is bad for maintainability... and just bad in general

c) std lib of a language is a special case here: without having memorized what it has to offer you're going to work many times slower due to having to google all the time

and so on.

You can either know a lot of languages and technologies and bet your career on ability to learn new things very quickly, or you can be content with one language and become a master in using it. In the latter case much of your skills do become tied to the language and particular technology, so just be sure to pick one which is not going to stop being popular in a year.