> rather it was that Boeing made software adjustments to make the plane fly like a regular 737 without training the pilots in these changes

No, this is a persistent and pernicious myth on HN – that the MCAS was some sort of “737 Emulator” intended to allow the plane’s customers to avoid pilot training.

In reality, during testing it was discovered that the engines’ new position caused the stick forces to invert in some situations during flight. “The stick forces invert” means that it becomes easier to pull into an aerodynamic stall than push away from it.

This fails a Fundamental Airworthiness Requirement that all commercial aircraft are required to conform with for certification.

Boeing’s “solution” was MCAS – using the stabilizer trim to automatically push the plane’s nose down as it approaches a stall (and therefore putting additional force on the stick that keeps it at all times easier to push away from the stall than pull into it).

The pilot training thing was just that they concealed the existence of MCAS from pilots out of fear that it would prompt calls for additional training.

tl;dr the problem was that the engine aerodynamics made the plane fundamentally uncertifiable without a software hack.

The fundamental problem is a lack of effective redundancy for bad sensors. They haven't fixed that. Software alone will not fix it. They've just implemented superficial procedures that don't address the real safety issue.