People could no longer learn hacking the way I did, by starting to work on a real operating system, making real improvements. In fact, in the 1980s I often came across newly graduated computer science majors who had never seen a real program in their lives. They had only seen toy exercises, school exercises, because every real program was a trade secret. They never had the experience of writing features for users to really use, and fixing the bugs that real users came across. The things you need to know to do real work.