Sheer numbers don't mean as much in the face of vastly superior weaponry. If the Soviets didn't keep pace with Western advances, they would be at a serious disadvantage.
Of course, but in many cases (BMP, T-64, SA-2, AT-3, R-7) they were ahead of the west. They built a technically advanced and massive army. Quantity was something the U.S. didn't consider necessary after the Vietnam War. At that point, the Soviets could've done the same. Except that a third of their army was deployed along their border with communist China and later they had a small problem in Afghanistan.