It's not meant to be. If it were, you'd see them spammed. Imagine playing against Soviet T1 as USF.
The purpose of the 221 is to provide some helpful extra firepower and anti-team weapon support before the 223 upgrade unlocks. The 223 upgrade turns it into an anti-infantry 222 with a load of useful support abilities. It can also turn into a cache when you're not using it to pay back its fuel cost.
It is, first and foremost, a utility vehicle. If you'd rather an anti-infantry shock unit, build the Luchs.
There's a world of difference between being useless and being a shock unit. The 221 is useful if you have it.
Opel trucks aren't fast, armoured and armed.
No one said it should be a shock unit, read my suggestions.
Opel truck is also cheaper and hardy used in 1vs1.
In 2vs2 cashes are simply better.