That sentence stuck out for me too. In my 15 years of solo programming experience it's not true: some things have gotten easier as I've gotten better and tackled more challenging problems. I don't think I stopped improving as a programmer when I turned 19.
But in my 5 years of working in an office with other coders and maintaining other people's code, it seems true enough. Although it can vary by project, most salaried programmers seem to be either good because they are engaged and have made a habit of improvement, or poor-to-adequate because they are disengaged habitually disinterested to the point where experience doesn't even sink in.
But in my 5 years of working in an office with other coders and maintaining other people's code, it seems true enough. Although it can vary by project, most salaried programmers seem to be either good because they are engaged and have made a habit of improvement, or poor-to-adequate because they are disengaged habitually disinterested to the point where experience doesn't even sink in.