It is not useless, at least not completely.
Having a big gun to shoot planes can be good, but size isn't everything.
It's not what you got, it's where you stick it.
Having an AA Bren is very useful, especially when you want to defend an outpost which is very remote, and don't have the means to transport anything larger than a bicycle.
And making wider roads is not always the answer. Having very narrow roads also excludes many wide vehicles, making infantry fighting necessary. Which would make sense in the forested areas of Normandy.
Then again, it should be historically accurate, so maybe it just shouldn't be done.
Cheers