I have been most interested in what the pilots that I know have said about it. And they did have some complaints, but the complaints were that the system behaved differently than what they were accustomed to. Boeing’s automatic stabilizer trim has worked the same way for around 40 years and none of them saw a good reason for the change in the way the system behaved. The flight characteristics of the system could have been changed to make up for the changes in the aerodynamics without altering the behavior of the way the stabilizer trim was used.
None of the pilots felt that the emergency procedures that they knew would not work if there was a malfunction. None of pilots that I know who have flown the 737 MAX have felt that it was an unsafe airplane. Sorry for the redundancy here, but almost all of them agreed that the software development on the new system was misguided because it changed the characteristics of a tried and true system unnecessarily and this contributed to the confusion that caused the pilots to lose control of their aircraft.
When the AOA vane that MCAS was using was working properly, MCAS probably also worked fine; it was when that single AOA vane went bad, probably indicating “full-scale high” that MCAS would drive the airplane into the ground.
That was a colossal human failure of the highest order.