Your suggestion of parsing out the in-code documentation would go a long way towards documenting the libraries, provided the documentation is of high quality. However, that still doesn't address the bigger question: how do I program in Pharo.
There's a book, "On to Smalltalk" that actually did a decent job of getting you started, but it's decades out of date now.
I think it would be not too much work to parse out this kind of information (Class comments, methods and method comments, structure etc) and spit it out as a web page that could be hosted somewhere. Do you think this would help, at least somewhat, to bridge the divide with new users?