You raise multiple questions. Some are assumptions which will take far too long to argue about, and therefore I will not dig into them. (I hope this discrimination is allowed :) )
How to measure etc. is a complex question. Of course, this is challenging work. This hard work is of high priority. That is central.
A call for action based of lack of knowledge is an interesting question. It again goes into multiple assumptions values etc. Should we assume no age differences in ability? this is bullocks. I happened to know a little about age differences in cognitive ability. Mostly it goes down. And most of the recently pupularized claims on age advantage are false. As far as the measured research shows.
Should we intervene in decisions of companies?
Generally, I think that evidence blind interventions are bad.
When you try to push low intelligence people into universities you not only do a disservice for everybody involved, but you lose many vastly better ways to improve their lot. I am sure some people feel differently, and it might be a hugely political discussion if so, with endless assumptions, and sub assumptions thrown in. Naturally leading to a dead end.
If there find reasonable reasons as to why tech companies ignore old folks, we might find much better ways how to integrate aging programmers in the tech world (by finding the kind of jobs more compatible for them etc. etc. all inside the tech world)