Gear icons

System Preferences icon in macOS 12 uses frustrating gears:

The reasons why they are frustrating:

1. The tooth's cross section is triangular.  
2. The teeth are narrower than the space between the teeth.
3. There is too many teeth.
   

Commonly, the teeth are curved to ensure good meshing of the gears:

Triangular/trapezoidal profile is commonly used only on gear racks:

or when we need the gears to come in to and out of engagement with each other without binding. If you use triangular profile, the torque transfer is irregular and there is be a lot of binding at some points and slop at others:

Furthermore, when two gears are made from the same material, it makes sense to use as wide teeth as the gap between the teeth to maximize the durability of the gearing.

Finally, the common count of teeth on a gear is commonly something around 20.