Most engineers (like every other profession and occupation) are mediocre. They look for job security in incompatibily. I once had a programming partner who refused to document his work. I asked why after pleading with him repeatedly to leave a trail behind him. "Job security." At another place, the programmers had a slogan "comments are for sissies." Same idea.
So if you take something like C and permute it slightly so that a C programmer doesn't have the skill, you now have something that makes you marketable over that person. You can snow the non-technical manager into believing that your older colleague can't cut it because he knows C and you know Javascript.
In this world of mediocrity there are a very small number of gems, people who work for the user, who strive to make their tech work better for people. That's a skill that develops over the years, you get better at it every decade, because you know more about people. When you're in your 20s you don't even have a clue about yourself.
And most of you commenting here are the mediocre kind of programmer (if you're programmers at all). The ones who are questioning the broad conclusions are the ones I'd want to work with, and I don't care how young or old they are. What I care about is if their minds are at work and if they can relate to other people as equals despite superficial differences like gender, race, age.