The S-400 isn't even really capable of shooting down the basic "quadcopter" drones, they're too small and fly far too low. You'd have to be extraordinarily lucky to be able to hit one.
I'm talking about Ukrainian shahed-equivalents here.
9M96E/E2 can be used to shoot down shahed-like UAVs, but it's not something you'd generally want to do. They don't exist in sufficient numbers and are far better suited for shooting down missiles. It's something you'd do as a last resort, when necessary. Not something you'd do to shoot down thousands of drones.
I'm talking about Ukrainian shahed-equivalents here.
9M96E/E2 can be used to shoot down shahed-like UAVs, but it's not something you'd generally want to do. They don't exist in sufficient numbers and are far better suited for shooting down missiles. It's something you'd do as a last resort, when necessary. Not something you'd do to shoot down thousands of drones.