I don't think there is anything ineffectual about it, it's 37mm, sure, but it's not like you hit something with a 1K bomb.... it's luck of the draw and 37mm isn't a guarantee of a kill. It's a pretty sure thing though if you can land rounds with it. Just aim for the wings. Nothing ineffectual about that.
A bomber can actually take a hit or two from Flak too, I've been low over a field in a B17 and taken hits from a Flakpanzer and survived. I think the key is it must be a hit in the fuselage, anything in the tail, or on the wings, means instant removal of that appendage 95% of the time. I think the only plane I've ever survived a hit from a Flak in that wasn't a bomber was an Il-2. I actually took 2 hits once and could have flown away but figured my luck was good and proceeded to take a 3rd hit.
Me'thinks you expect the 37mm to be a magic bullet, but it's not. That said, it's damn effective when you know how to hit with it.
-Soda