The biggest problems with the Pirate and the later Banshee, Panther, Shooting Star and Scorpion was their designer's sticking to old technology more than the poor early engines. By the end or WWII, the German designers had basically dropped the straight wing in all of their designs due to the success of the swept wings used in the Swallow and Komet. It wasn't until the F-86 reached operational status, in 1949, that the US had a fighter with swept wings and could reach the speed of sound. Granted, the F-86 used a better engine than the Pirate, having 4000lbs of thrust to the Pirates 3000, but it was the Sabre's swept wing that made it so much superior