Or instead pilots could be trained to monitor speed and power on the approach like most good pilots already do
Very true.
Actually remove absolutely all automation, make it a simple stick& rudder aircraft and all "weaknesses" are gone. Additional safeguards and other "warnings" only compound the problem by making pilot more dependent on them. More warnings, more audio sounds, more flashing lights don't necessarily make it safer, basic fact known to anybody who studied human factors in the cockpit. Therefore it has been recognized long time ago that absolutely nothing can replace monitoring such basic things like speed, power and attitude. These guys failed to monitor all 3 of them which is pretty astounding if you think about it.