First of all, thanks, Slam for the video of the AA pilot's briefing/presentation.
My feeling is that AA was reacting to the Cali accident, when entering a confusing waypoint turned the plane the wrong way. Although realizing the jet was turning the wrong way, and then coming back to the desired course, they continued the descent. The end result was still heartbreaking to me, as I knew the A/C very well.
The issue is not the FBW systems. I can't think of any heavy planes that have flown since the 70's that had exclusive mechanical linkages to the control surfaces. Seems most had simple hydraulic valves at the bottom of the yoke that moved actuators via pressure. There were some real mechanical connections like cables, pulleys, pushrods and such for some surfaces. But the primary control surfaces, the big ones, were pure hydraulics. Feedback seemed to be springs and such to provide "feel". Same as I flew for many years in lites.