Yeah that’s cool - saw a better one shooting down incoming rockets - but like most defenses, they have limited ammo, and the enemy knowing that can overwhelm the best defense. A heavy mortar attack would guarantee a few rounds would land on your miniguns.
Well, “limited” ammo is relative. One advantage that the big LPWS part of C-RAM has over its seagoing sibling is that it isn’t limited to just the ammo on a relatively small mount - IIRC, it has thousands and thousands of rounds of ammo available to it.
It also is capable, as part of the C-RAM system as a whole, of directing counterbattery. It isn’t perfect, but there have been heavy mortar attacks on the Green Zone and other areas defended by C-RAM and they didn’t cause much damage.