[The 34/76]... scales terribly and after 6-7 minutes, when heavier axis units arrive (most notably tigers and Panthers) they become absolute trash, specially if you enemy is not brain dead and supports their tanks well.
In much the same way wehrmacht T3 and OKW puma's aren't all that great against heavy allied armour. We've all seen the PiV v. IS2 film. People go Panther or >, in order to counter allied medium armor.