This is reminding me of RUSE, in the sense that as in that game here the function of AA is not to actually destroy planes, or even to deny areas of the map to enemy planes...
AA is actually here to allow you to establish local air superiority over your ground units.
You need to use fighters if you want to destroy enemy planes. What AA allows you to do is ensure that you'll win if the opponent sends fighters against your fighters. Your AA panics his fighters, your fighters then go on to destroy them.
It is much more difficult to establish air superiority when you have no AA!
I actually really like this, it's different from Wargame where a single AA piece can render your planes useless. Which was actually really lazy gameplay, other than SEAD you could generally destroy enemy planes just by leaving your AA to itself. Now in Steel Division if you want to destroy planes you actually have to be proactive about it. Get yourself a couple of fighters and always keep a CAP up. You might not prevent your ground units being bombed, but you will be able to take out his 160 pt plane...