Why was it SO difficult for Boeing to design a system which endowed the aircraft with proper handling and stall protection when the Concorde designers created such a system over 50 years ago ?
On Concorde there was a high angle of attack system which retrimmed the elevons and triggered the stick shaker, signalled from the ADCs.
In addition there were TWO anti stall systems where the superstab system applied up to 8 degrees of down elevon and at speeds of 140 k and below the superstab system applied 4 degrees of down elevon.
One might think that with modern electronics and vastly more experience of FBW systems as on the 777 and 787 a better MCAS equivalent would have been a very straightforward task.
This is a basic description of the system as described in Brian Trubshaws excellent book, Concorde, the complete Inside Story, well worth a read by Boeing engineers and regulators, indeed anyone with any interest in the MCAS system and its shortcomings.