Like I said, don't think bout the KT t34 thing. It sounded really cool in head but it came out wrong and that just confused everyone to thinking about Heavies. Just forget I said that. Think about if you have a t34/85 or P4j how likely are you to make said standard t34's or P4's(i mean for this it's obvious when no money for the former very specific sitch).
I play moslty 2v2's(cause I play with friend most of the time) and the occasional 1v1's other wise(I know the meta is very different in those 2 modes)
Yes, and I already defocused from your KT example and used heavies as an example that your claim (strong units are favored over cost efficient ones) is not true.
The T34/85 is better yes, but it is still exceptionally cost efficient, mostly because it is quite hard to lose with its increased health. P4J? Maybe.
Two years ago (heck or is it even 3?) we had SU76 spam metas, where you'd just get 3+ of these and bombard Axis out of any position while dealing with their armor at the same time. Players chose that strat although the SU85 was readily available at the time, because they would get both AI and AT of a cheap unit instead of investing into an expensive combination of SU85 and Katyusha.
But let me get one thing straight:
I am not saying that straight upgrades via doctrines did not exist, they definitely do. What I am saying is that it is perfectly possible to offer doctrinal abilities/units as alternatives instead of upgrades and those are absolutely viable.
And design wise this is the superior choice. Otherwise the game boils down to who exploits his doctrinal unit first, not who exploits his whole army the best. Non-doc strats became unviable as well. If core armies are not able to deal with everything (even doctrinal units) that are being thrown at them, we run into an endless loop of patching the weaknesses or overbuffing their stock units as compensation as we can see with Brits for the last years.
The game can work with doctrinal units being straight up OP, yes, but it is easier and smarter design/balance wise to add doctrinal abilities as strategic alternatives.