Not so much if they are on chip. It's reliable with discrete components if the parasitic is just backing an external component. For example, a capacitor acros

Not so much if they are on chip. It's reliable with discrete components if the parasitic is just backing an external component. For example, a capacitor across a junction contributes most of the capacitance so the capacitance of the junction is just a small parallel capacitance. I agree that it's not good to use a "bare" parasitic in a discrete circuit, unless the circuit is very insensitive to its value.