VP isn't a big deal at all. It's basically a gearbox.
Not unless you have a geared engine, but even in that case, seldom does that have any bearing on the propeller...which isn't a gearbox. It can be thought of somewhat like a transmission, but even that is overcomplication.
So long as the user knows that setting the RPM with the propeller control establishes a propeller RPM that will stay the same within published limits, when enough engine power is applied to keep it in the governing range...good enough.
Whereas a gearbox serves to change the RPM from one end to the other due to gearing ratio, the constant speed propeller (the most common kind of variable pitch prop) is far more simple...merely using oil pressure to move a piston to change blade angle. The blade angle loads the engine and propeller to keep it's speed in check in simple installations, or unloads the engine and propeller by decreasing blade angle in the even the propeller speed decreases.