It needs a very good pilot and a very good front gunner and a very good rear gunner to keep a heavy bomber alive and doing any significant damage. On small maps it doesn’t even matter - you can LMG them and they can’t escape.
Yes, a good crew needs a good player to kill them, but it only needs one on AA (and with LMG) or one in a fighter to kill 3 or 4 in a heavy bomber. Hardly seems to favour the bomber.
If you’ve seen a vid with a heavy bomber with a high KD then you’ve seen a match where the other team just didn’t try to bring it down.