Why secondary guns were not the easy autoloader target

Why did navies not begin by autoloading smaller secondary or cruiser-caliber guns?

Smaller shells helped, but multiple ammunition types and the machinery needed to select them made reliable automation difficult with period technology.

Dual-purpose weapons may need high explosive, armor-piercing, and star shell, making selection and ready stowage a central design problem. Smaller ammunition reduced the lifting burden but did not remove the need to choose the correct round. Period machinery lacked modern barcode identification and flexible automated picking, so humans still had to supervise key steps. An autoloader was therefore possible, but its complexity could erase much of the apparent advantage of starting with a smaller gun.