I guess this depends on the trading method.
Someone that isn't profitable could teach you about MACDs, crossovers, exchanges, options etc. etc.
None of this would make you profitable.
In my quest, I paid 3 people for training. 1 of them couldn't trade (although he had an ego the size of a house) and was of no use at all. He was also the most expensive. The other 2 could trade, they understood the nuances of their method. They could answer questions. They could show examples & tell you what was going through their head at the time.
Perhaps the particular area of trading I went into was different from others. I can say hand on heart that if you cannot trade this way, it would be impossible for you to teach it. It requires you to have been there and done it before you could impart knowledge of the experience.
I mean, I had a Maths teacher that I was particularly fond of... but what, I should ignore what she says because she hasn't won the Fields medal? Is a student only capable of matching their teachers level of achievement?
I understand this view. The thing is - we don't need the BEST trader to teach us. We need a proficient trader. We don't need an award winner, we just need to avoid the failures, the sim traders and the never-traded.
Whilst we are doing analogies. Would we expect someone well versed in driving theory but with no actual practice to teach us how to drive ?
Anyway - I can say hand on heart that for what I do, experience is the first pre-requisite in being able to teach the methods. The second is empathy and the third is the ability to teach.