What I meant is that instead of having a teacher - a person you interact with, and who is at least aware of your existence and learning goals - you find existing material published by experts and use that to guide your learning - without ever having to be in contact with them.

What about feedback ? Isn't it an important shortcut ?

Some kind of feedback is required. If you can get personal feedback, from 1:1 interactions with a teacher, all power to you. But many people can't, and have to seek out feedback on case-by-case basis (e.g. by sharing their work on-line), and/or from non-living sources (e.g. your solution working is a form of feedback in itself, quite fertile if you pay attention to it).