The circumstances here were predictable based on the design of the systems. A proper evaluation of the system - as designed - would have revealed the opportunity for a malfunctioning radio altimeter to cause a reduction to idle thrust in flight.
So what do you suggest?
Millions of $ redesigning and retrofitting a new radalt system to the entire 737NG fleet?
Or reminding pilots that when they are not getting the thrust they need from the autothrottle, they may switch it off and apply thrust manually?