I've worked with some extremely smart older people, who did some awesome stuff in the 70s/80s. My impression is that usually, in my experience, they're very jaded and set in their ways. They seem to like to do things their own way and give the impression that they're infallible because they deconstructed an x stack in y decade, and complain about the cyclical nature of programming. They also seem to usually not go out to happy hours/events with the team to get to know one another as often, so they're excluded a little more, which leads to fewer people getting to know them.
I have seen exceptions, one of the PMs on my current team must be in her 60s and she exhibits none of the characteristics above and is a really amazing, smart person. It's just that most of the older people I have personally met seem to have the traits I described above. This would give me a little pause when choosing between equal candidates for, say, an angular dev position where both candidates have equal experience in the stack, but the older one has the baggage(?) of having been a programmer since the 70s and knows COBOL or something. I would likely have an unconscious bias to hire the younger one.
I have seen exceptions, one of the PMs on my current team must be in her 60s and she exhibits none of the characteristics above and is a really amazing, smart person. It's just that most of the older people I have personally met seem to have the traits I described above. This would give me a little pause when choosing between equal candidates for, say, an angular dev position where both candidates have equal experience in the stack, but the older one has the baggage(?) of having been a programmer since the 70s and knows COBOL or something. I would likely have an unconscious bias to hire the younger one.