The DO have downsides, problem is they dont have clear downsides against OKW and its not persistant downsides.
They suffers badly against Ost sniper, they suffers against Ost mortar and so on. Pretty much they suffers from anything but mainline inf early on, at the same time OKW has ONLY mainline inf early on.
But on the other hand, they have the strongest late game and mid game, especially in team games. At least OKW that I play against. Also, the guy that built 2x sturms and 2x kubel. It's a pretty good build vs USF. A couple of days ago I went vs that build on Across the Rheine. On the beach side, sturms went to heavy cover fuel, kubel was behind them and other sturms charged my heavy cover (VP sandbag) rifleman and won the engagement (5v4,5v3,4v3,3v3,3v2,2v2 - I retreat). Then my 2nd rifles coming to help were pushed back by 2 model sturms and kubel. Basically I had no chance with echelons -> rifle -> rifle -> rifle vs sturms->sturms->kubel->kubel on that map which is green cover rich around fuel and VP, especially with sturms being starting unit vs my echelons.
While I agree that volks before the upgrade are lackluster, they are also cheaper. Until the vet and upgrade, you really need to keep them long range, cover only. But that's why you need to play smart. I've seen 2 good OKW players win vs 2 of my brit allies (3OKW vs 2xbrit + my USF on whiteball). Basically in each VP "lane" they used volks as bait for IS and flanked with sturms. Both fell for that.
Point is, while they are weaker, you have to adapt playing vs different factions. Don't force all the fights. IN 1v1 it is most prominent. The ability to gauge which fights and when to take them are probably the most important thing in 1v1. You play as OKW vs UKF on a map which favors UKF?
Be smart. I think there is even a loading screen tip that says the best commanders know which fights to take. Something like that. It's true that in early game, chances are OKW will lose to UKF, but you have to play around those chances.
Don't complain about the hand you've been dealt, learn to play with it.