"I'm sorry to say you are making so many unwarranted assumptions and are displaying a huge bias."

You seem really upset, and your argument seems almost entirely emotional.

"People don't know things because they've never encountered them."

I'm not sure what this has to do with anything. Could you explain how this applies to your argument?

If, after 45 years, you don't have a basic grasp of CS , and you were doing a CS job for 45 years, it doesn't seem likely to me you will gain one soon.

If you were a math professor for the past 10 years, yeah, i can understand that.

"People don't stop learning as they age, "

Whether this is true or not, after 45 years, they haven't learned any better than the guy with 1 year of experience.

"What people have achieved or not in their careers is not your business, when you hire."

????
I made an argument based on current skill level and likely future skill level.

"You hire based on competence."

Sorry, For lower levels, people hire based on both current competence, and likely future competence.
Otherwise, nobody would get hired at lower levels.

Lawyers out of law school are incompetent. Firms hire them based on what their future rate of competence is likely to be.

Same with every software engineer out of college.
Nobody hires for the long term based on straight current competence. It would make no sense (short term hiring, it often does).

Even if you were right, then they wouldn't get hired anyway, because they weren't at the level one would expect after being at it for so many years. That's what you seem to miss. It's your job to push yourself and grow. You can't seriously expect that if you haven't grown in 45 years, someone should take a chance on you expecting that in the next two, you are going to buck all that and grow.

"Assuming that people don't grow at 99 because they've been at it for 45 years is stupid and ageist."
You haven't explained why. your argument above is 100% unpersuasive.

I'm not even assuming. I'm pointing out that they haven't grown. Whether they can or not is actually even somewhat besides the point.

They haven't. So either they aren't pushing themselves, or they can't. At some point, it doesn't matter. I don't want people that don't do either. if you suddenly decide, after 45 years of stagnation, you want to grow in your career, you can't expect everyone else to believe it is going to happen.

Let's say it was neither, and it was because they had a sick child for 45 years they needed to care for.
I still can't hire them at a level the other people with 45 years of experience have.
I can't know this, either. I can only make risk calculations based on the data i have. Your argument is "we shouldn't be allowed to make calculations about people". Which would make hiring essentially random.

If i can't hire them at the level they belong, i have to compare them against lower levels i could hire them at based on their current and future predicted competence. When you do this calculation, it does not come out in favor of the guy with 45 years experience.

"In fact, it's perfectly equivalent to say "I don't hire women in their 30s because they'll want to have children".
"

This is a 100% non-responsive, emotional swipe for no reason. it's completely and utterly false in every way, and honestly, it makes me simply not want to have a discussion with you.
So i'm out on this part of the thread.