I found a new term recently, which shares a lot of the origins of what you’re describing. That term is “Resume languages” (Americanism). i.e a language (or it could be just as easily be any skill) which is learnt or focused on purely for the perceived effect it will have on your CV.
The pejorative context in which found it, was describing the false economy of companies that hire young, brilliant, single — but, critically, fickle — developers fresh out of university. People who the company think will plug a knowledge vacuum, but are in fact only eager in doing whatever is hip, not whatever is actually the often dreary practicalities of the job.
The upshot of this is that it’s nice to think “If only I knew X” but the reality is that you already know W, Y and Z and companies value you being able to connect the dots between those three just as much as Hipster JS framework X.