That’s your opportunity. You don’t need to become the “expert” in a particular glue language, but the more you can improve your glue language skill set, the more valuable you are to a wide variety of developers.
alert() for input
validation, try stretching your legs with Node.js. If you still don’t know what
a pipe is, dive into shell scripting a bit further. These languages have been
around for ages, and will continue to be around for years to come.
Look into other common areas, too: they needn’t even be languages. Make sure you understand JSON and XML. Look into how you can expose your web frameworks over REST. Consider real-time streaming protocols in your API. These are concepts that transcend arbitrary language choice.
The usage of cross-discipline, cross-culture glue languages is only going to grow. Embrace it. Get out of your language comfort zone and work at becoming a better programming citizen. The more our communities can work in glue languages, the better we can work together.