> But ... they won't know the libraries let alone their intricacies and idiosyncrasies etc
triggered a related thought (also closely related to recent "how do you learn effectively?" and "I'm exhausted/burned out, what do I do?" HN threads):
In my most recent job-search, I found this type of expectation/requirement (specifically regarding deep (down to idiosyncratic) library (aka framework) knowledge & experience) to be the most off-putting. The likelihood that I will have used a specific library in the ecosystem your team/company has chosen in its pursuit of "teh hotness" is (to put it mildly) low, but I'm certain that my resume will be discarded, or worse, an interview process spun up but doomed because I'll be unable to regurgitate library documentation chapter and verse (much less idiosyncrasies (many of which may be version specific).
The proliferation of libraries/frameworks seems to be exponential; how would I ever acquire deep knowledge of the complete set of same that are considered "today's hotness" (both today and of the past N years) in an language ecosystem which I have extensive experience and familiarity with? My current employer/team has made its language and framework choices, and I'm bound to them for (typically) years, and I focus (for years) on being productive in that context. Am I expected (in the context of my next job) to have spent my non-working hours gaining/maintaining knowledge of both the contemporaneous competing frameworks (which current employer/team didn't choose, but came in close second, etc.) as well as each "new hotness" that comes along? The alternative appears to be that my future employment possibilities are continually being reduced/narrowed as the set of libraries/frameworks in popular use expands (exponentially) while my knowledge remains tightly focused within the domain. Even if I was willing to make an investment in self-study to learn a new library/framework well, given the above-described circumstance, what would be my criteria to make a wise choice? And if presented with the same question 6 months later, what is the likelihood I would make the same choice? I'm pretty sure the answer is not "100%".
In practice, I simply did not apply to the vast majority of job listings which I would have considered myself otherwise a good fit (i.e. could immediately grow into), due to this factor.