I'm pretty sure that everything I was "taught" is now unsuccessful...
I'll agree with this statement only in as far as the market conditions have changed to the point where the old methods I learned do not work now, and it has to do with ranging and price action.
I "graduated" from my trading training at about the beginning of 2017. I was prepared for what the market was giving me. Then the market went apeshit by the time I felt comfortable enough and started making good money in beginning of last year.
I remember it being a ghastly and rare day when an equity future ranged more than a few hundred bucks in a day. Now, it is ranging multiples of that. My training did not prepare me for that, so I have had to try to adapt.
The lessons I learned are still applicable, but the timescale to apply them are now "tighter", if that makes any sense. I am the world's worst student because I have not been following my mentor's teachings as close as I could or should, but that is pretty much because I am my own creature, and I will flesh out into my own being when it comes to trading.
If I stuck to his teachings closer? I might be in a better place now than I am.
Had I not branched out on my own and found something that worked better for me? I might be in a worse place than I am now.
It is a most curious phenomenon.
As to the OP's point...
...from those who have proven profitable retail trading is possible...
I
know it is. All we have to do is follow our plan and be smart with the implementation of our trading system.