You need to keep in mind the role that the Carbine was intended to fill.
It was a service support weapon that was to be issued to rear area personell, crew served weapon teams, vehicle drivers, cooks, clerks, administrative, artillery, etc, etc, etc. Basically anyone that would have been issued a pistol or SMG because a full sized rifle like the M1903 or M1Garand where the full sized .30-06 rifle would be to cumbersome or not needed.
When troops saw the carbine and appreciated how handy they were and light, they adoped it as a front line rifle and thats where the complaints started. Soldiers complained of lack of accuracy, lack of power, and lack of range with the .30 Carbine. Had they been using a .30-06 rifle, they would have no complaints at all, but they expected a .30 Carbine to do the same job of the .30-06 round. Simply not going to work.
The Carbine emerged from WWII with an excellent reputation for reliability and was one of the weapons that helped us win the war, but the soldiers either loved it or hated it.
For the ones that hated it, if you asked them what they would prefer to be armed with in combat....either the M1911 .45 pistol or the .30 Carbine which was designed to replace the pistol, I'd bet every one of those combat vets would choose the carbine.
Don