The way I see it is this - each faction has weaknesses.
Ost lacks true "elite" infantry and a 60 range TD but Grens are pretty solid throughout the game and they have great support weapons (and the PAK is incredible).
OKW lacks great support weapons but have an otherwise solid infantry backbone (Volk + SP early game is extremely strong), great light vehicles (luchs and 251 both incredible), and a good tank core (Jp4, super P4, Panther). They're also able to lock down sections of the map with T4 and repair stupid fast late game.
Soviets lack decent mainline infantry. Penals are reasonable, but still cannot compete with LMG Grens/Obers/or even highly vetted Stg Volks and are locked in T1. The real mainline Sov infantry that can compete (guards) are locked behind doctrines and are expensive. Soviets probably have the strongest commander based units/abilities (T34/85s, 120mm, Guards, IS2, PPSH, IL2, ISU) to supplement otherwise average-okay core units (the normal mortar is passable but nothing amazing, Maxim has its place but is no MG42, ZIS is good but isn't a PAK, etc).
USF generally lacks indirect fire but has incredible mainline infantry (like OKW, but even stronger really once they get BARs), flexible light vehicles, and a punishing tank core (HE Sherman is a wipe machine). USF also suffers from important units being locked by tech (AT gun, 50cals).
UKF has a poor early field presence, lacks pushing power for most of the game, lacks mobile indirect fire, lacks infantry snares (except in 1 doctrine), but has a disgusting late game arsenal (commandos, double upgunned 5 man tommies, great AT gun, etc).
So really the argument you're making could be made about any faction, just pick a different unit.
Why are Guards so good but Pgrens are so average?
Why is the Ost mortar so good but the USF mortar so average?
Why is the PAK so good but the USF At gun so bad?
Grass is always greener, focus on the strengths of OKW if that's the Axis faction you want to play (early aggression/MP efficient infantry, great light vehicles, and a great late game if you can keep stuff alive). Good luck vs UKF and Sovs as OKW though