Yes, for sure those are not simple, but they can be taught, right? Just a simple ratio of expected TP-to-SL of 3-to-1 would save a lot of people, but of course there are way more advanced methods. Still even the ones who mastered it, don't necessarily earn profits (with consideration of all fees, taxes, inflation, real rates, etc.)
Since trading is one of the most difficult professions and very long in terms of formation, the issue of learning in percentage is the same as that of successful traders. You can prepare theoretically, but practically hardly. Here psychology is also important, psychotype, approach and so on. This cannot be taught.
True and no I think. You can skip most (not all) the hard-way learning path by learning from others what works and what doesn't, what worked before and what won't in the future. Just like with basics - yes, you can directly deposit $100 and start learning and after a year personally find out that there's head & shoulders pattern, there's overconfidence bias, etc. Or you can read it, learn it, see it, and you already skipped that 1 year of practice.
It will not work like that, having studied other people's mistakes you will only understand superficially, but the best understanding for a trader comes through his own series of trial and error. This is best stored in the head. That is, your negative experience will push you to find the right solution faster than someone else's. Until you make a mistake yourself, you will not understand. So it will never be possible to analyze other people's mistakes and completely avoid them. All traders have always lost their money at least once. And so it will continue. You have to go through this.