You wouldn't generally let a C-RAM fire at a low angle over a city. And even if you did, the problem of how many of these you need for decent coverage becomes

You wouldn't generally let a C-RAM fire at a low angle over a city. And even if you did, the problem of how many of these you need for decent coverage becomes large, because there's no ideal placement that doesn't involve shooting straight at friendly things from some approach vectors. A CIWS is not a reasonable way to stop drone attacks on civilian targets.