The Johnson is a real departure from the guns before it. Had it come along before the Garrand had such a following it might have been adopted but the Garrand looks more like a military rifle which helped it more than you might think. It was normal looking. The Johnson was described to me as a pot belly pig. I shot one many years ago and found it, or atleast that one was very reliable. Accuracy was decent with open sights and we ran perhaps two rounds through it without a malfunction. Of course gun never malfunction on the range, just when you really, really need them.
The problem often encountered in new weapon design is the limitation imposed before the first design is put to paper. When you decide to keep all designs to 30-06, as a logistics decision to keep supplies to a bare number, you limit the gun. Smaller rounds could increase the capacity but you question the possible decrease of lethality. Case in point was the Carbine which was just a pistol round in a long gun.
If you read about Johnson you will find he was a interesting fellow with a bit of a checkered past. In many ways he was a fellow who thought in 3-D like John Browning. He could visualize how things worked together, make a working model and alter it to refine it better.
