Not true.
In the PTO, the M3 75mm cannon was so powerful that it could blow a hole clean through Japanese tanks, in and out. The AP ammo was so devistating that often HE were used by preferance. At El Alamein it outclassed (numerically) most German tanks deployed. Versions with wet stowage (denoted by a (W) after the model and ammendment code) and a 76.2mm cannon were on par with the Panzer IVHs we have in game right now. The M4A3E8 76(w) with wide tracks, wet stowage, and a 76.2mm gun was every bit as good as the T-34/85.
The British version with the 17 pounder AT gun could kill Tigers with ease out to 2,000 meters, and that is with standard APC ammo.