The problem was mode confusion not the inability to fly a visual approach.
It is irrelevant. The problem was much more basic - inability to monitor approach. This is far more basic than any mode confusion. If you think that something will work for you (like A/T) but you fail to monitor its operation it frankly puts your basic airmanship into question. Regardless if they were 'confused' or they weren't confused but A/T was say defective they still failed in their basic duties as pilots. Even if a pilot suffers from a temporary blackout and forgot what mode does what it is still his duty to monitor basic parameters like speed, altitude, etc., specially if he is on a short final. He/she can quickly 'unconfuse' himself but turning off all automatics. Bubbers44 summed it above in a single sentence quite well.