CLD is not the best at lowering noise from outside the car. That would be MLV.
CLD is for lowering the resonant frequency of a panel by adding mass and stiffness.
MLV is for blocking the transmission of sound from outside to inside. Or any dense heavy product placed as a continuous layer.
No one product is an all in one solution for noise in a car. Too bad it's not so simple, but it makes sense when you take into account its fluid dynamics and psycho acoustics at play here.