OKW is fine, they have crappy vehicles and no lategame infantry.
I think you're playing some other OKW then the rest of the community.
The OKW I play with have fuel free capping, durable vehicle, cost effective lights, mediums and stock heavy, together with doctrinal self spotting panther and unit eraser that relic for whatever reason thought was a good idea to increase its range while keeping its pinpoint accuracy, but somehow the same was bit no-no for allied counterpart and B4.
OKW meds and heavies just got a cost increase without performance changes, because of how powerful they are and how early they arrive.
So, where are these crappy vehicle you're playing with? I might try that custom mod to see your POV.