the Soviets suffered greater losses of AFVs on the Eastern Front than the Germans, but that's because 1. the Germans attacked first, and chewed their way through a sizable number of light or obsolete tanks like the T-26, T-28, and BT-series during the first two years of the war, and 2. the Soviets produced more AFV's than the Germans overall period. 45,000 lost out of over 50,000 produced is pretty wretched, but it also tells a very important story: the Soviets were able to churn out over 50,000 examples of this all-around heavily armed and well armored tank of all variants. Compare that to the Panther which, while definitely more technologically sophisticated, only reached 6000 total produced. Even the legendary Tiger, which could kill the T-34 at distance before it even had a chance to engage, only reached less than 1400 produced. Oh, and the Germans had to split these between two fronts.
Also, for all the technological sophistication and superiority of the Panther...the majority of them broke down and had to be withdrawn from combat during their initial debut at Kursk. Meanwhile those "unreliabe" T-34s were able scurry across the battlefield and rip and tear the Panzerwaffe