NO!
Well, depending on the mod you're using. GW lowered their accuracy, not sure about NYGM, but stock flak gunner shot pretty well.
It also depends on the flak you're using. The first light flak couldn't hit a person 2 metres off, so... Later flak and heavy flak make everything easier.
Imagine U-Flak with 3X Quand *insert right flak gun name here*!
Now that would shoot anything down!