Not to downplay this but wasnt this the case for basically any major power that developed and fielded tanks back then? development moved so quick in this field compared to nowadays (at least in the general design, guns, ammunition and machinery categories) that obviously a lot of stuff was lacking, like tiger 2s (at least some, dunno if that flaw was dealt with later) couldnt or could barely turn their turret when on uneven ground, the transmissions struggling heavily with the massive weight of those monsters (i mean they weight more than most modern day mbts, kinda crazy to think about) and in general, especially for russia quantity was understandably more important than, lets just say, fielding 200 insanely strong but hard to transport, repair and maintain heavy tanks in form of something like a tiger 2 (instead of maybe 1000 t34s) considering the huge country they had to defend. And even then, the t34 general design rly aint that bad, considering the hull and also the turret are both heavily or at least somewhat angled on most sides, something the german tanks of the same time and class were heavily behind with and US tanks and GB ones also didnt implement in that Form, while possibly excelling in other metrics like gun performance, reliability and whatnot.
Also its probably even for historical experts hard to reconstruct nowadays what lead them to design the tanks the way they are, why they cut back on other stuff, its known at least under what immense time pressure all of this must have taken place. but no one here was part of the political decisions behind all of that so…so much about it is just guestimates and to say nowadays: the armor was subpar is like: yeah ofc now, 80 years later thats easy to say. But there were very real reasons for most of that stuff back then.
And Even then, to think about that the t34 was built in what? 1940? and in 1946 they built the IS-7 prototypes which were most likely the best or at least one of the very best tanks in the entire world back then (if only they werent too expensive) and ofc not battle proven and still prototypes is kinda crazy to me. absolute nuts development in just 6 years no?