As others have pointed out, ATRs worked just fine for the most part, it's just that their employment and the tactics prevalent at the beginning of the war were the problem. The Soviets' success with the PTRD shows that it wasn't the dead-end weapon many seem to think it is. The Boys ATR was successful against armored cars, halftracks, and other light vehicles, but less so against tanks.
France 1940 might have looked very different if the French and Belgians had a good ATR that was distributed at the platoon or squad level. Remember that one of the main factors in the success of the German Blitzkreig was the use of halftracks and armored cars, which ATRs would have had little trouble destroying.