This assumes that the 60-year-old programmer has even learned .NET programming
This article is utter trash for that statement alone, what a blatant piece of age discrimination. If most 60 year olds learned COBOL then many will sunset with COBOL, those that do stay relevant with the newest technologies are exactly the type of developers who a smart person would want to hire. The reason being, that algorithms don't change, math does not change and also we have a dirty little secret that we keep reinventing the wheel on new stacks. So a 60 year old that has been through 3-4 stacks is going to have seen a lot more problems and solved a lot more problems that mirror problems that his organization is going to experience. They are also going to have mastered and learned a lot more foundational stuff. To assume that all programming knowledge is temporal is to stack the decks in favor of a certain viewpoint and ignores reality. Arguing that said 60 year old will be bitter is just a cop-out for lack of any sound argument.