I agree with the fact that most trading systems are not really a good thing, personally I'm against any fixed trading system, and simply know that none can work, if not for a limited period of time.
The reason for this is that the market conditions are constantly changing.
Markets are not constantly changing in any radical way. The small gradual changes that do occur just mean you need to have robustness in the system. Big changes when everything goes upside down do happen but those are usually once per decade (last one way in 2008-9).
