Frustrating I know but if they get it fixed quickly or a crew member becomes available sooner than expected; then suddenly flight recovery is at the mercy of the FAA giving up an unscheduled slot, how close the crew is to timing out, how bad dispatch needs the plane elsewhere, or even if there is an airport curfew at the other end. Maybe BA in the UK is different, but all things being equal random USA airline buttons it up and they are going without you.

Generally speaking AA in the USA delay announcements are made with a caveat to stay close and check back. Seen it many times and made way more often than not.

Last experience PHX-LAX on an RJ the departure time kept bouncing up and down like a pogo stick. The gate agent advised check back every 10-15 minutes. Ended up they got a crew after all and rescheduled close to the original time. Boarded but now short 20 people on a capacity flight. Held for half an hour till the people on the plane started getting restless about their connections. Buttoned up and left with lots of empty seats.

Yes it could be better but until it is some things just are.