Personally I think a mix of formal Education, Mentorship and Self-Learning is the best way to learn complex domains

I agree. I'm not against formal education at all, but was instead giving a counterexample. It is possible to become educated almost solely through formal education despite that perhaps not being the primary goal of the institutions you attend.

Harvard, for instance, is a fantastic place to learn things despite the fact that it is also practically a hedge fund, a gatekeeping organization, and several other things that are unrelated to educating people.

I consider myself an autodidact but I have a degree and without getting one likely would not have rounded out my background knowledge in computer science.