...then the airline has a Duty of Care to have a system which identifies such issues, assesses them and then, if necessary, to put additional mitigation in place - such as, say, banning the use of 33. AA may have looked at this and, if so, their Safety Case should explain why they concluded it was safe.
I refer to the case of Lufthansa identifying night visual separation as a safety issue and deciding not to allow it, then one of their aircraft having to divert from SFO because of this decision. AA banning DCA 33 might have had the same kind of result.
Anyway, after 72 pages it seems fairly clear that separating IFR from VFR at night by visual means inside the circuit pattern of a major airport is not a great plan. This could happen anywhere in the US and it would be an interesting exercise for the NTSB/FAA to see how many separation losses there were at other airports, as they have the software to do that. It is easy to fixate on this accident and the immediate environment when similar setups exist all over the place. It’s not just about helicopters and the military - civil and fixed wing on that kind of clearance could be just as risk-bearing.