Thank you @aurelienpierre for bringing up this fascinating topic. On a personal note I’m not bothered by the technical nature and movie-length of your videos. Please continue!
I think your point is that learning digital photography is not simple, but worth the effort. I agree completely. But hiding in your essay, there is another more important question for the Darktable community: For whom should we make Darktable?
A real strength of free software is as a tool for learning. Darktable is an excellent example of that. But I think that we (as the community) could be better teachers. Or more precisely, provide better tools for self learning.
@aurelienpierre , you bring up your 12 years as piano student. One thing we could learn from the hundreds of years of experience in the art of teaching music instruments is how to progress the student from beginner to expert. As I understand it, musical students progress from one level to another. Each level comes with specific skills the student must master to progress. This system makes it easier for the student to know what to learn, and for the teacher to know what to teach.
But learning digital photography by acquiring a camera and downloading Darktable is like learning to swim by being thrown into an ice-cold river. You need skills in colour management, colour theory, the mechanics of cameras, knowledge of how a digital sensor works, learning about how to manage an effective processing workflow, etc. And since OS X and Windows are second class citizens (as they should be), you are encouraged to learn Linux as well.
In other words, you have to begin your journey by learning what you need to learn, which is not pedagogical. Furthermore, the sink-or-swim approach makes it harder to contribute to the community by teaching other people about Darktable, since everyone has to invent their own lecture plan.
How could we do better? One solution is to collect the video and text resources out there and organize them into lessons with progressing difficulty. Each level should have clear goals. These resources should be reachable by a big button on the Darktable home page.
Getting your pictures off your camera and organizing them for easy retrieval in the future.
Importing pictures into Darktable. Basic editing of a jpeg: Cropping according to the rule of thirds, adjusting white level using a grey card, straightening the horizon.
Sharing your picture (exporting for prints vs exporting for the web).
Calibrating your monitor using open source tools. Understanding how colours work in your camera, your monitor and printer
Level 5: etc etc.