Re: Is this to say that the 737 max is too difficult to fly manually?
Some routinely executed flight manoeuvres and stuff that were routine on 737s prior to MAX become unacceptably risky without computer assistace/override on the MAX family. Up to you to decide whether than equates to "too difficult to fly manually".
Further reading via:
https://theaircurrent.com/aviation-safety/what-is-the-boeing-737-max-maneuvering-characteristics-augmentation-system-mcas-jt610/ (article published November 2018, after LionAir but well before Ethiopia).