Problem is, you look at OKW, which should be late-war (45) units etc, vs something like soviet AT which are from 1939 and you begin to see the difference.
While it's true a lot of their units are outdated, you're exaggerating it. The Soviets and Germans were based on mid-late war when CoH2 came out, and the Germans were better off due to the technology they had at that time. The game's shifted to late-end war now, and the Soviets look quite outdated. Ostheer, not so much due to the fact that their tech didn't change as drastically from 1943-1945, and OKW released with all the 1945 goodies. USF is in the same boat as 1944 Soviets due to their stubborn doctrine refusing Heavy Armour and restricting AT armed Tanks (they favored HE).
T-70: 1942 - 1943 (T-70's portrayal in CoH2 is actually positively exaggerated)
SU-76: 1942 - 1945 (Most produced vehicle after the T-34, most were made in 1944)
M5 HT: 1942 - 1945 (Quad AA mount variants saw use 1944 - 1945)
SU-85: 1943 - 1944 (Soviet Army's primary purpose-built tank destroyer)
T-34/76: 1942 - 1944 (Only the T-34 M1943, which is the model portrayed in-game)
They're not as outdated as you think, the only
really odd-one-out is the T-34/76 which was largely replaced by the T-34/85. Followed by the T-70, which was replaced by the T-34/76 (or '85 if they had extra). People often cite the SU-85 as being outdated, but the SU-100 didn't arrive until late 1944 and was in much smaller numbers than the SU-85.