Agreed, but reading between the lines of these ads, there's a world of difference between an ad which is "we're looking for a great developer who will use <language X> to do [...]" and "we're looking for a <language X> Developer".

In my experience, the latter presentation tends to actively drive away the best candidates, and communicates a lack of understanding of the job to be done. This is not an absolute; sometimes you really do need a specific skillset. For example, one great company I worked at almost universally hired solid developers regardless of particular checkbox skills. We knew that the good ones would come up to speed, and we'd often benefit greatly from cross-pollination from differing backgrounds. However, there were definite instances where we needed a true specialist, e.g. in a specific, deep platform UI framework. Then we sought and found solid developers who were also top of their game in the needed skills.

In the latter ad copy above, a "<language X> Developer" often has the connotation not of a targeted specialist hire, e.g. "expert in <language X>". Instead it comes across as lazy recruiting: "warm body who checks off this box".