They didn't say it requires saints and/or geniuses to follow the advice in TFA, they said that people will often twist good advice in bad directions because they have ulterior motives. This is true regardless of how difficult actually implementing the advice would be.
The advice in TFA basically boils down to "don't pendulum, try to find a good middle ground between extremes", which shouldn't require either a saint or a genius.
The system works for him. Moreover, I expect it likely works well enough for some people. Humans are a rather heterogeneous lot. Any system of universal applicability is going to be extremely limited in its ability to provide tactical insight.
The advice in TFA basically boils down to "don't pendulum, try to find a good middle ground between extremes", which shouldn't require either a saint or a genius.