> As evidence that the applicants are, at every stage, correctly reacting to the situation: I have received positive responses (and, later, job offers) by applying to roles for which I am only mostly qualified...

Even fifteen years ago, I was getting advice from grizzled (programming industry) veterans of the form

  If you match even half of what they're asking for, apply. Most of the time, those lists are put together by HR; and even if the list is completely accurate, they're never going to find anyone that meets all those requirements. The ad is asking for the *ideal* candidate. The smart companies know they're going to have to settle for less. Let *them* filter *you* out.

I've interviewed a fair bit, both in and out of Silicon Valley. I've had exactly two interviews where the folks hiring knew exactly what they wanted. All the others were like "Well, we need a programmer to do programmer stuff, IDK.".