There is literally nothing wrong with soviet lategame power, and their mediums and TDs are perfectly fine. Units aren't required to be OP just cause they're USF
No USF major tier is the only tier where literally every unit in said tier gives a headache to your opponet more than they should. There are other factions who have nice things, but other factions things also have drawbacks.
Then why do you see the T34-85s and even the IS2 being the main consideration when it comes to your Commander selection as Soviets? Besides having Shock Troops or Guards available.
Units aren't required to be OP just cause they're USF, I agree with that but if T4 isn't good enough then USF falls apart entirely, because USF has nothing further beyond the Major Tier (or tied to the Major Tier) besides the almighty Pershing. All the other call-ins are specialized units, you can't solely rely upon, you gonna have to tech up eventually in a regular game.
The Sherman is their generalist, the Jackson their TD and the Scott their alternative to rocket artillery. And that's it for their lategame, each unit does it's job because it's the best you are going to get, when going Airborne, Recon, Infantry, etc.
Let USF lategame too, it's not like it's overwhelmingly powerful early game anymore, or won't be once Pathfinders get nerfed and the Toilet Truck is neutered.
Unless GREnadiers prove to be overwhelmingly powerful