Trading courses and coaches are useless- true or not

How to understand the phrase "the simpler the trading system, the better"?

What is the degree of simplicity here? Or the simplicity here is not what I thought, just use a few indicators, so what do you think of this sentence?

Why do we still fail to trade after learning so many trading indicators?

What are the advantages of weekly trading over daily trading?

Seeking expert guidance, what is the difference between left-hand trading and right-hand trading?

I have had a few positions liquidated recently, but fortunately the losses were not very large. I would like to ask everyone, is there any way to prevent liquidation? Is there any trading discipline?