Especially when it's a new aircraft, perhaps pilots need time to adjust, same as when you and I get in to a new car, it may have different response when you hit the gas, different mirrors, different sounds, different steering wheel sensitivity, etc.
This again pushes the blame back onto Boeing who insisted pilots didn't need to be retrained / trained up against this model aircraft as it would've meant extra expenditure by the airlines.
There's also been quite a few of these type of stalls documented in the past (eg. where the pitot tubes failed).
Also, pilots should be prepared to experience faulty sensors as they could fail at any time, no matter what model aircraft they are flying, no?
MCAS is not autopilot, and is not affected by autopilot system status. Indeed it is only enabled when the autopilot is off. And typical things you'd do to override autopilot, like applying stick input, do not override MCAS. The pilots did literally what you suggested their first reaction would be, and it wasn't sufficient to prevent fatal crashes.
if it works, don't change it - sadly nowadays that's not true anymore for tech industry, they change things for the sake of change.
Idling cars at stoplights doesn't work. It adds unneeded pollution and wastes fuel. If there were an efficient way to avoid that, it would be stupid not to. That's why they changed it.
What shocks me is that this is the first you've heard of it. You've never heard the car next to you shut off when they pull up to a light?