I have been in the military, long before the A-10 came along, and can assure you that their prop driven predecessors were often quite a comfort.
I have heard that as well. When my Dad was in Korea, they occasionally benefited from napalm and rocket/strafing runs by F-4U Corsairs. Skyraiders were after his time in the service, but both turned out to be low and slow, able to hit targets with a surprising amount of ordnance, and able to absorb some battle damage and keep going. I see the A-10 as an updated version of that, With not only the 'gun', but an incredible and varied ordnance load out (something for everyone on their naughty list).

It can carry up to 16,000 pounds of ordnance, some 2-4 times what a B-17 could (depending on the distance covered by the B-17 and fuel needed).
We haven't mentioned the modified B-25s of WWII (with up to 13 forward facing .50 caliber machine guns, or an array of 20 and/or 37 mm cannons), mainly used against Japanese shipping, which deserve a mention as ancestral cousins to heavily armed purpose build CAS aircraft. Theirs is a different story.
And "Puff" (Spooky, AC-47) and Spectre (AC-130A) and Ghostrider (AC-130J) aircraft are in a class all their own, too.