I have many years of experience in trading both in the CBOT bond pit and by computer, as well as designing profitable systems and backtesting. There is nothing magic about Dennis' system or Donchian Channels.
They did what anyone willing to work can do: Find a repeatable method that has a positive expectancy, apply aggressive money management rules to it, and trade it faithfully and consistently.

They picked people that they thought had personalities that would allow them to stick to the rules, which is critical for any "system".

Where things break down, and the problem with trading an otherwise profitable system that you havent developed yourself (with incorporated knowledge of yourself and your risk tolerance)
is that your brain won't let you follow ALL the rules, ALL the time.

For the vast majority of people, trading a system that someone else has developed is usually a fools game. It might be profitable on paper, and for the person that developed it, but if its
style and rules aren't compatible with your particular brand of "fear and greed" (which we all have), you're very likely to lose money.