the problem is expectancy. If you have a system that wins 30% of the time but wins really big when it does, that could mean losing money for 8 months in a row and then winning for 3 months (and still be in good profit).
people just can't hack the long losing periods so they give up, or start gambling, breaking all the rules. They just need to tough it out and follow the plan.
Absolutely. Swapping systems at low points in them is the quickest way to incur a loss. When I started crypto trading I dumped coins left, right and centre every time they dropped in value. It took a few months to realise how the cycles worked (and how much profit I had been throwing away).