> Humans are capable of learning a variety of different skills, even if they have already learned one. Articles like this treat them like specially made parts that are only suited for one thing.
that has always been true, however looking at my father and friends' experiences it seems it was a lot easier in the past to switch to completely different careers due to entry level jobs being widely available, previous experience not being as important, career paths where joining entry level and being "promoted from within" were the norm rather than the exception, and the "youth cult" where a new graduate is seen as a safer hiring bet compared to a 40+ hire did not exist. In addition the workplace was seen as the workplace, the place you go to work, which you leave and go home to live your life, it wasn't seen as a "24/7 place" where you have to "culture fit" and you are always available.
Nowadays everybody wants previous experience, and the specific experience for your particular position too, because you have to "hit the ground running" from day 1 and the "a single bad hire can doom your company". You also should not be too old, or too experienced, be good at the interviewing gauntlet (which often has little to do with the actual job) and you must fit in whatever arbitrary "culture" the prospective company has. This means it can get difficult to switch jobs in the same industry, let alone move to something unrelated.
Talking about our field, everybody knows that if you have a 10-15 years solid track record in several different languages and environments you could be adding value in most companies after a couple months ramp-up, but would you even be invited to an interview if you don't have a specific X years of experience in language Y with Z1,Z2,Z3... libraries? I mean, some job postings I've seen even express preference for candidates familiar with a particular IDE, if that is not treating people like single-purpose machines I don't know what is...
If you are in your 50s, with health insurance tied to your disappearing job, knowing there is no safety net and you're a few months away from living on the sidewalk, don't you think you would be desperate? If there was a safety net where you could live somewhere while you are retrained and have a chance, of course you would take it, but in today's world that doesn't seem to be in the cards.