It crashed because the system that was making it behave that way failed. The MCAS did not get correct data, did not react well, was not easily deduced to be the problem, and was not easily disabled.

Training and technical improvements can resolve these problems and it's ready to fly. If that's still deemed too risky then Boeing can remove the behavior modifications with training and certification as a completely new design. It was this cost that they were trying to avoid through emulation but clearly not done in a safe enough manner.