You're describing the opposite extreme. Most people are aware that they need to strike a balance: be aware of your own marketability versus just doing enough but not burning themselves up.
Being more or less productive is defined by - in no particular order - your salary, workplace culture (a due sense of agency and feeling respected,...), your own intrinsic motivation to choose a particular career path and personal circumstances that keep one at a job (usually household debt in any way shape or form).
Contrast that with the fact that digital tech today is an industry in which a large part of your toolbox and knowledge is perceived as "obsolete" within a short time (1 or 2 years). The net result is that most people burn themselves out in a race they can't hope to ever finish.
So the notion that "you must keep up at all costs" is unsustainable to put it mildly.
> They’ll probably get small raises every year, and perhaps the occasional promotion based on years served. But that’s really as good as it gets for them.
And that's totally valid. Why do people need to forcefully "climb the ladder" through promotions? A promotion isn't just a reward, it's often a serious career change that comes with serious challenges.
If someone wants to move vertically in a particular role throughout their career - say, as a developer - then that's totally fine too.
If someone isn't interested in spending time at home working on OSS projects - even when their employer provides incentives - then that's fine as well.
> They’re usually very friendly to work with, but they’ll have skills that are 10-20 years out of date, and mediocre at that. Eventually even the slow moving large organisations start to outpace their own personal development, and they get left looking for jobs that don’t really exist anymore.
That's a bias. Not every large organisation operates like a silicon valley style start up. Not every organisation has "building cutting-edge software" as a primary mission.
Banks, airlines, public institutions,... don't operate on short timescales (5 or 10 years), they operate on long timescales (20 to 50 years out). They aren't interested in shiny tech, they are interested in robust & proven solutions that last a very long time.
A large chunk of software engineering is boring and slow moving for a good reason: because breaking things comes with serious real world consequences.
Case in point: there's still demand for COBOL and Perl programmers. You can perfectly build a career in as an expert in those areas.
> I worked with a guy a few years ago, and all he’d ever really done was Swing projects. He added me on LinkedIn a few months ago, he’s been working at a cinema for the past two years, trying to find a new Swing project to work on.
Anecdotal.
If he works at a cinema, that might be because he can't simply move to another area with more swing projects (family or other concerns), or because he genuinely got tired and wanted something else, or because he just doesn't know how to promote himself properly - it's not his strong suit - and he turned to LinkedIn just recently.
Unless this is a close friend, you do not know half of this person's life and their decisions. Assuming x because y, well, that's just jumping to conclusions, isn't it then?