I don't see anything wrong with that either, but I think the quote is phrasing it slightly wrong. Here's how I would write that sentence:
"Employers justify shunting aside mid-career programmers on the ground that they lack the motivation to develop skills in, among other thing, the latest software languages."
The problem is that this lack of motivation won't show up until the programmer is midcareer.
When they graduated from college/trade school/etc, they were likely trained in some the latest technologies and languages. Based solely on skill set, they looked motivated enough; maybe not as much as some, but certainly more so than the mid-career programmer was just kicked to the curb for not knowing anything from more recent than five years ago.
But they stagnated, because they really weren't motivated or interested in what they learned beyond the predictable payout it guaranteed.. They went to school because they needed that structure to force themselves to learn material they were told would be highly lucrative. Learning more about their field was hard and not at all satisfying, so they made the gamble that they could coast on what they learned in school until retirement.
Unfortunately, technology moves fast enough that their gamble blew up in their face. They wouldn't be able to see it coming either, because the structure they embed themselves in to increase the odds of their gamble would be equally phobic of new advances. The realization would happen suddenly, likely due to an internal shake-up either by new management or the same old technology no longer being good enough.
The problem is that a course in the hot new language du jour isn't enough. The problem is that their lack of motivation is now painfully obvious to everyone. They aren't the least bit curious about new advancements, otherwise they would know something about them. The knowledge they get from the training course will inevitably become obsolete again in another few years, because they'll never supplement or expand upon it.
This is the real reason for the shunting, as I see it. And I, like paulbaumgart, see nothing wrong with it.