Another consideration is time, stamina, and commitments. A person fresh out of college doesn't necessarily have anything holding them back from devoting time and resources to learn and master something. A person who's even younger will have more time and possibly more family support/coercion (how many violin prodigies do you think picked up the violin entirely of their own volition?)
Someone in their 40s may have a time-consuming job and a family to support, which precludes ditching the time-consuming job in favor of putting in long hours to master something. Maybe they can only spare an hour or two a week, and maybe they're so exhausted from work that every now and then they can't even do that.
Older adults may be more risk-averse, but that doesn't mean they're incapable of mastering something, just that they're less likely to choose to do so.
On the other hand, unscrupulous employers tend to exploit younger employees by giving them more hours, for a few reasons (fortunately, I've never worked at a company like this, but I know I dodged a bullet).
"You don't have a family to go home to, so of course you won't object to working until 9pm every day."
"There are a gazillion fresh-out-of-college people with your exact skillset I can hire to replace you in a heartbeat, and you don't yet have the professional reputation to easily find another job."
"You don't have a nest egg built up yet, so if you quit on me or I fire you, enjoy defaulting on your lease and couch surfing until you find something else."
Someone in their 40s may have a time-consuming job and a family to support, which precludes ditching the time-consuming job in favor of putting in long hours to master something. Maybe they can only spare an hour or two a week, and maybe they're so exhausted from work that every now and then they can't even do that.
Older adults may be more risk-averse, but that doesn't mean they're incapable of mastering something, just that they're less likely to choose to do so.