"But learning alone is slow, difficult, and doing so usually proves demotivating."
That may be true for some people, but for many others (like me, and I suspect a lot of other HN readers) learning alone is our preferred method of learning.
How do you define "alone"? What I've found is that learning alone is a very high percentage of overall time spent, but being alone, meaning relying solely on google / stack exchange, is vastly more difficult than having a conversation with someone either in person or virtually.