Lower income but cheaper tech and more powerful units. It's not lower income - nothing, it's lower income - best tech and best units.
I have 1400h with CoH2 and I saw bunkers, a saw sometimes 2 bunkers, but Ive never ever seen something what you are describing.
Wires, sandbags, flak emplacement, bunkers, mines - this is defense. It requires micro, tactic and planning.
Schwerer has nothing to do with those things.
It actually happens in the very replay I posted like 10 minutes ago, and OKW's units are just expensive as every other factions units but more so due to the fuel reduction tacked on. OKW can get vehicles at the door faster with cheaper teching but replacing them becomes tricky if you lose them to fast.
Lower income has to come with some sort of thing to make up for it, since making a faction that's just objectively worse isn't very attractive.
and the flak emplacement is a joke, killed by any unit with grenades, mines don't require skill, demo's do, wire and sandbags are piss easy to use to cut off sectors.
Nothing defense related requires that much thinking, the Schwer is just the big daddy of defense but it still dies like any other emplacement. Get armor/indirect and play smart, the schwer will be no issue for you in that case.
Shutting down area's of the map is stupid easy as USF, I'm kind of shocked you haven't ever FP spammed.