Player input is not something that should be scaled by delta time. If the player moved the mouse +50 units on the X axis this frame, then that’s how much he moved it. It is already independent of frame rate. Instead it depends on the player moving/pressing the inputs.
So to control how sensitive the mouse movement is for a player, you multiply the input value by another value.
InputValue * Sensitivity = ScaledInputValue
InputValue * 0.5f = half as sensitive
InputValue * 2.f = twice as sensitive