A systematic approach is one thing, a dead set system is something else.
eg. even a "Rating" is a system in the sense that for example many pre-post markets are set by a computer.

Most systems are adulterated to suit the individual, eg take my PPM (Partypoopers Plum Movers) responsible for providing the 500-1 shot last Saturday (BF SP)

Original rules:
Sat Metro only 5 states
Take the first horse working up from the bottom weight that is a distance winner or course and distance winner.

Thats it! (the 500-1 shot fit perfect absolute bottom weight with a "D" after its form)

But that system has been tweaked by many since then to include all Metro meets, or even all meets, some even back the first 2 that have a D or C.

Some only bet when the selection IS bottom weight etc etc.

The point being is that most methods of betting are indeed a sophisticated (or not ) result of a systematic approach.

Apart from the dart or pin that is.

My contention is that most systems work, BUT they don't work all the time.....

the best you can hope is that it works while you are betting with real money!