In the Ethiopian crash the crew followed the runaway trim check list but didn't recover. The issue seems have been that the aircraft was going to fast so they couldn't turn the manual trim adjuster. But that isn't mentioned on the runaway checklist (http://www.b737.org.uk/runawaystab.htm)
OK a different crew might have figured that and slowed down but not crashing should not be that tricky really.
Then they did A) re-enabled electric trim (and MCAS) B) while still low, C) touched the trim button for a second, and didn't adjust anywhere close to proper trim, and D) left electric trim/MCAS on.
Not to mention, from your source, the FCTM says:
> Excessive airloads on the stabilizer may require effort by both pilots to correct the mis-trim. In extreme cases it may be necessary to aerodynamically relieve the airloads to allow manual trimming. Accelerate or decelerate towards the in-trim speed while attempting to trim manually.
This isn't true. If you follow the runaway trim procedure, you recover. Pilots in the US are required to demonstrate the runaway trim procedure as part of a type rating checkride.
Aggravating factors are, IMO:
1) Even well-trained aircrews getting a runaway trim condition on takeoff are not guaranteed to show the same performance as on their checkride day.
2) Not all jurisdictions require this demonstration.
3) The MCAS could fail in a way that could be surprising and not seem exactly like normal runaway trim (intermittency).
4) This test of "can you handle runaway trim?" was much more frequent than the normal causes of a stuck switch or actuator.
I think #3-4 is the big issue. While better trained crews could address the others, MCAS has the ability to fail in a way that it only does stuff when the crew isn't looking. There's nothing that can address this but system redundancy.