The 85 isn't a specialized version of the 76mm it's just a bigger version
Yeah I also disagree that the T-34-85 is a sidegrade. It's straight up a better T-34-76. The only situations I can think of where a player might go with the 76 instead is when they can't wait for the extra fuel, when they just need a tank to force enemy infantry off the flanks (in which case a T-34-76 is more cost efficient) or when they need a tank to ram with. In all other cases, the T-34-85 is simply the superior choice. Which is completely fine in my opinion. Doctrinal things shouldn't be better per default, but it's fine if some things are to some extend. As long as they aren't that much better that the doctrine becomes a no brainer pick. Soviet doctrine picks have a healthy amount of diversity at the moment. Could the T-34-85 have worked as more of a specialized vehicle (for example a tank hunter like the Panther)? Sure. But the current design works just as well.
In that regard I also don't agree that the SVTs aren't a sidegrade compared to the 7 men upgrade. I think it is. SVTs come sooner and are better for the mid game while 7 men are better late game. It's down to player strategy and preference which one to pick, demonstrated by the fact that both are meta and both are used very often. The same is true for Panzerfusiliers and Volksgrenadiers. 5 men Grens were supposed to offer the same choice, but ultimately their increased durability has made it a favourable upgrade over the LMG 42. But again I don't think this is bad per se as the doctrine is designed on purpose to offer very good infantry bonuses but little else. So even if the VSL upgrade itself is a bit of a no brainer pick because it's better than the stock upgrade, the doctrine isn't.