The marginal return to experience is minimal after a decade or so, particularly when it comes to the average software job. If you have decades of experience, you need to be in a higher leverage position (either consulting or management) to get appropriate pay for the position.
This doesn't make tech ageist. My local grocery store also doesn't pay the senior cashiers any more than the high school ones.
If all you need is someone with a few years' experience, the younger candidates are probably going to be willing to work longer hours, for less money, than the older candidates.
In other words, why pay a 20+ year veteran a lot of money to do Rails programming when a recent college grad knows enough to do a decent job, and can be paid an entry-level salary? Not every engineer on a team needs to be senior.
I suspect this is also good career advice: if you don't want to compete with entry-level programmers for jobs, specialize in an area where more experience makes you a more desirable job candidate.
Mind that the parent poster didn't claim that experience was not valuable in web applications; just that there were diminished returns.
Embedded systems programming is far more architecture and device specific than web applications are, thankfully. Embedded systems programming requires a much large body of knowledge: chipsets and their features, device-specific options, the behavior of the RTOS (if there is one), esoteric configurations in the cross-compiler or build tool, ability to interactively debug (read the instruction set, use the interface (JTAG, etc), cope with interrupts), ability to thrive with extreme resource limits, and write comprehensive tests with a nearly-exhaustive test plan; since a final release can't be rolled back once customers have purchased it.
This isn't because of some inherent superiority or prestige of embedded systems programming (salaries are lower across the board compared to backend applications programmers), it's just plain more complicated.
A 20-year senior backend programmer should really have progressed to an architect or principal engineer role at that point in her career. An embedded systems developer with 20 years of experience is more typical because of its inherent complexity.
He didn't say it wasn't valuable. He said it might not be more valuable than 5 years' experience, presumably because technologies change so quickly in web programming. I don't agree with that, but he certainly wasn't being ageist.
The marginal return to experience is minimal after a decade or so, particularly when it comes to the average software job. If you have decades of experience, you need to be in a higher leverage position (either consulting or management) to get appropriate pay for the position.
This doesn't make tech ageist. My local grocery store also doesn't pay the senior cashiers any more than the high school ones.