Although solenoid valves serve a purpose, they do have limitations.
They are instant on, and can not be feathered, unless you have the proportional solenoid valves.
Solenoids fail just like anything else, due to corrosion, heat, loose solenoid on the valve, they have to be torqued just so, and spike voltage, low voltage.
While holding the solenoid on, they may draw 1 to 3 amps.
Debris/trash in the hyd fluid may restrict proper operation of the solenoid valve, sticky plunger, jammed plunger etc.
On out Power-Tracs, most of the PTO circuits use a solenoid valveto run the hyd motor on the attachment. The operation is almost instant. Full on or full off.
Some of the solenoid valves have an optional way of energizing the valve with no voltage. A small pin on the end of the solenoid. You push on it to operate the valve.
They are an excellent way of diverting fluid between circuits. The activation of the solenoid is also convenient as to where the switch is mounted. The solenoid valve can be almost anywhere