That's a huge stretch. The fix was to work around a certification requirement that the control forces shouldn't decrease as the aircraft approaches the stall. This is a long way away from the aircraft being inherently unstable.
Fehrm, a former jet-fighter pilot and an aeronautical engineer: https://www.seattletimes.com/business/boeing-aerospace/faa-e...
That said there are airliners out there which are unstable in the longitudinal axis and require a yaw damper to prevent Dutch roll.
My intention was not to claim 737 MAX had the same aerodynamic nature as, say, F-16, but in the scope of the discussion point out that fixing instabilities with flight software can be made to work reliably.
The main argument was that it was inherently a bad idea to require computer assist to maintain stability and decades of military planes demonstrate that you can engineers such systems to be more or less fault safe.
There was a sibling comment somewhere in this post that stated that airbus doesn't introduce a layer between the pilot and the aircraft. This couldn't be further from the truth (assuming normal control laws). Applying full back stick on an airbus will hold the aircraft right on the edge of a stall. Applying full left or right on the stick will neatly roll the aircraft to 60 degrees of bank. Releasing the stick at this point will roll the aircraft back to a perfect 30 banked turn in the same direction. This isn't normal behaviour by any stretch.
If anything I think Boeing are suffering from not going to fly by wire control earlier. That would have made this whole subsystem irrelevant. You'd just apply the desired behaviour in the response curves in the control software.