Hiring older developers is the fastest way to put hundreds of security holes in your software. That's reality, people. They just simply don't keep up and don't have modern college training in the latest security threats and program hacking methods.
Remember that when you become an older developer.
Snide aside, while your argument has some merit, there is a flaw in your assignment of blame. Development is not a static process, you need to continually update your skills in order top remain relevant. And one of the major impediments to updating skills is companies not providing an environment when such updating is valued.
You could counter with a "well they can do it on their own time", but the rebuttal to that is two fold:
1. Older workers have a life outside of work and have other things to do.
2. Anyone who is forced to update skills outside of work hours because their company won't support them in work hours is eventually going to say "Fuck it, why should this company benefit from my self improvement - I'm going elsewhere."
And there you are .. back to square one. But of course an older worker would have seen this from the outset, due to all the workplace experience that they have gathered.