But wasn’t it necessary for the men to get close to the cave openings in order to blast ‘em with flame throwers; whereas, with high powered guns, a safe distance could be maintained?
There were openings where tanks couldn't reach. Those did require infantry assaults. Artillery was always available to the troops; however, plunging fire wouldn't go into the openings.
Daisy cutters are today's answer to caves; and, they are way too big for cannons. Air power is the most effective weapon by a long shot.