B24's had six gunners per plane, B17's had 8 gunners per plane. In formations you can do the multiplication. You can bet your plane they would shred anything that came up on their six nice and slow and steady like some lazier or less informed fighter pilots. Accuracy a joke and not realistic? I don't think so. It's not realistic to think that you can come up on a heavily armed bomber and just sit there at the six and shoot it.
Hit Lancasters from below between the outboard and inboard engine, it goes down without a good portion of the wing. It's guns never had a chance to touch you. Perform a high angles attack on it and stay the heck out of it's six and the worst you face is .303's and they rarely touch you.
B17's and B24's easily catch fire. Attack one from below and you should be toast. Attack one from above at high angles and you've got 50's to face, but again they can hardly touch you if you do it correctly.
If more than one fighter attacks in coordinated fashion from opposite sides, the bombers are toast.
The guns aren't too accurate. There's only one or two guys shooting at you and they can't be at every gun position at once. Think of it as facing a guy at each gun position on each bomber and assume they're half way competent at what they're doing. Approach them as a real fighter pilot would and you'll find the results are realistic. Approach them as a newb would and you'll find those results are realistic too.