The T.34 did well what it did, but it had no real innovations to offer, despite sloped armour. The optics were inferior, the gun was good, but had no really decisive punch, transmissions remained to be a critical item, of the earlier models of the T-34 more tanks got lost than were lost to German fire. The commander had to serve as gunner as well, which led to inferior battle awareness. When the Panzer-IV appeared, the initial superiority of the T-34 started to falter, and the Panther and Tiger simply were superior designs. But when they started to enter the battlefield, the T-34 had been started by the Soviets to be used in big numbers, and no longer as individual lead vehicles. Shooting ranges of German versus Soviet tanks showed the German tanks being superior in most comparsions, due to better optics (precision) and reach of the gun.
The biggest advantage of the T-34 was its armour which initially was a tough bug for the Germans' PAKs, and its good mobility and small silhouette.
The T-34 is one of the leading historic actors in WWII, no doubt. But it was not that innovative that I would rate it as a decisive benchmark of tank building in that era. And after the Tigers and Panthers and 5.xx calibre PAKs appeared, it more and more depended on being operated in huge numbers - like the Americans had orders that their small light tanks, the Shermans, should not engage German Tigers if they had not at least a 7:1 numerical superiority.
Darauf ein Zeiss! 