Here's a video of older 737 simulator with runaway stabilizer - starts just before 3 minutes in -
Think for a minute (no you don't have that long...) - how fast can the automation incorrectly trim and put you in a nose-down/high speed position. What's the best reaction time one could expect from a pilot to recognize what is happening and take the appropriate action?
Then, think - now you've got to manually crank the trim back, while still flying the plane manually and taking care of everything else at low altitude --- I'd sure like to see a simulator video of this situation with the Lion or Ethiopian situation and see how reasonable it is to expect a flight crew to deal with this situation....