The claim that knowledge workers spend all day answering email and do nothing to focus on self-improvement is just plain bullshit. The fact that we're presently using a website that essentially serves as a crowdsourced, real-time trade journal counters that argument. The existence and wild success of engineering-focused conferences counters that argument. The proliferation of easy-to-access information for professional growth allows for a self-selecting group of people to improve their lot in life just by picking up some new skills and getting some experience with them. You can learn a new skill literally by browsing the Internet these days. As such, I don't really view the knowledge worker as a person at risk of stagnation without actually making an effort to be lazy.

There are some people who feel that they already know everything they need to know, and don't want to better themselves. It is entirely attitudinal, and in no way unique to the "knowledge worker" classification. I would argue the problem is far more significant in other industries, such as manufacturing and other heavy industry. When a specific kind of job replaced by a machine, or an entire industry gets outsourced to another country, the individuals previously responsible for that kind of work are likely not to have been trained for any other function. That would probably be a better audience for this kind of thing, compared to people who spend their free time reading about new technologies and playing with them on the weekends for fun.