Hi, t_harangi!
I´m sorry for the late reply! I had to work non-stop on some IT projects for the last three weeks So, I didn´t have time to write anything on the LingQ forum.
" we need structure and discipline and good habits, that’s why I usually recommend Assimil to most people who are starting out "
I agree Assimil´s approach is great. I recommend it myself all the time.
But simply picking a method, tool / app, book, etc. without knowing what you are doing and why you are doing it should never be the first step on the learning journey [to avoid a misunderstanding here: “You” refers to (independent) first time language learners, not to experienced language learners who already have several languages under their belt. ]
Instead, “successful” learners spend a considerable amount of time learning about language learning / acquisition in general. Unfortunately, many learners (beyond language learning!) don´t do this! They often rush ahead completely blindly, without really knowing what they are doing and why they (should) be doing it:
- “Oh, just give me a smartphone app!”.
- “Oh, just give me some phrases to memorize so I can reach a B2 level in no time.”
- “Goals? What kind of goals? I just want to be fluent.”
- “I’ll just attend a language class once a week”,
etc. etc.
The result is (way too often) a complete mess of half-knowledge (and that’s a euphemism!), bad habits, no plan/structure, no goals, etc. - and a lot of “excuses” for inadequate results and failures.
Good teachers / coaches know this - and act accordingly.
“these list of “devil in the details” questions you ask are retroactive,”
Of course. I´ve spent decades learning / teaching practical skills (languages, math, and a bit of programming). And these questions are the result of what I´ve tried out myself (as a learner), what I´ve read in the (academic) literature, and what I´ve tested as a teacher.
No independent first-time learner is able to ask (and answer) most of these “devil in the details” questions. Ortherwise, he / she would already be an advanced learner 
However, people (companies) pay professional teachers / coaches because they should know this stuff.
Especially the whole “strong Why?” thing you often bring up. I never had a “why?” it has always been “just because.” I’ve learned three languages just because I felt like it.
All learners I had in teaching languages, math, or programming needed these practical skills for very specific purposes (tests, exams, their work, studying at a university, etc.). So, the “why” was obvious. Unfortunately, it wasn´t always a “strong” why so some of them tended to give up very quickly when things became “uncomfortable”…
“Just because” isn´t a good reason for most learners because many of them will give up quickly as soon as they realize that they have to invest a lot of time, energy, and money to really master a challenging skill. So, you may be the exception to the rule
“as we feel our way along and course correct from time to time”
When you´ve spent enough time on educating yourself beforehand, you don´t “feel” your way.! Rather, you “know” what you´re doing and why you´re doing it!
And, of course, you always correct your course because that´s how self-directed learning works.
BTW:
An acquaintance of mine would say in this context:
“But, Peter. You´re preaching all the time the “Lean Startup” / agile way. So, classical planning (which includes anticipation, plans, goal-setting, etc.) is obsolete, isn´t it?”
Well, it depends on the kind of problems we have to deal with.
- Traditional “complicated” problems (in stable environments) can be solved with classical planning approaches.
- In contrast, evolutionary and agile approaches with short time horizons, many experiments, etc. are a better fit for dealing with complex problems in volatile environments (a case in point: building an innovative startup).
Therefore, being “agile” is for professionals who “know” their stuff and have to deal with a lot of factual, social, and temporal complexity that can´t be reduced to basic (simple) principles (as is often the case with complicated problems).
In other words, “being agile” is not the same as just “feeling your way” and rushing forward blindly . Otherwise, “being agile” would simply be the same as “being clueless”
