Why a port can be the wrong place to unload landing ships

Why can unloading amphibious ships over a beach be safer than using a port?

A beach offers location choice, clearer air-defence arcs and direct ramp use, while a port can expose ships and require slow crane unloading.

A ship unloading in a known port is easy for an opponent to locate and target. Urban surroundings also complicate defensive weapons and identification. Going over a beach lets commanders choose the site and use ramps directly, though a suitable port can move greater volume. In the case discussed, high quays required cranes and defeated the landing ship's drive-off design, removing much of the port's theoretical advantage.