What you described has nothing to do with flexibility.
Flexibility is ability to adapt to situation on the battlefield which OKW and OST do the best.
End of story.
T1 soviets - no AT gun.
USF AT mines? No AT gun.
Variation of units is just variation, not flexibility.
Well, if your micro can't handle with coordination of 4 tanks at once, I feel sorry for you.
But in hands of a quite good player 4 Pz4 are more deadly than Tiger or Elephant.
Same for T34. I have in loadout doctrines without ISU, IS, T34/85, only T34/76 spam and guess what, it's damn deadly. It's way easier to deal with 1 huge target like IS2, than with few smaller coming from all sides.
But if you can't handle IS2, ISU, T34/85, Tiger, Elephnat, Panther meta, that's your problem.
I break meta very often and Im quite susscefull with this
Have not use any call in in 4v2 for 2 weeks as soviets - all wins. It's all about micro rather than A-move with IS2, and my 6-8 T34/76 are always more devastating than 2 IS2s.
It's not a matter of micro, but your PIV's are going to get raped HARD when facing Jacksons and IS2/T34/85s. You need the Elefant to break up enemy armor units like the ISU and IS2 because your dinky little PIV's aren't going to do shit to his 122mm gun and 375 frontal armor IS2.
6 T34's are overwhelming, but fuck if your ever going to get that in anything lower than 4's, and if can micro their heavies your T34's are going to be sitting in the scrap heap.
Soviets have a buttload of variation in what toys/strats they have to play with that are viable, so what if you don't have an AT gun in t1? If your doing call in trickery go t1 - t2 and wait for support. Or just go t2 and get support weapons that you back up with cons/shocks, get a guard or two sometimes to deal with OKW light vehicles.
You can break away from the meta, but someone who knows how to counter you will pistol whip you with better micro and unit choice.