....Faced with competition from Airbus, they made the decision to update the 737 range rather than develop an all-new aircraft.....
......in order to remain competitive with Airbus' fundamentally more modern design, there have had to be fudges and fixes, to make the tech fit a 50-year old airframe design......
Don't forget that the A320 design is itself more than 30 years old.
The advantage the Airbus design has, is that it was designed with a fly-by-wire control system from the beginning.
Not unlike Boeing with the 737-MAX, Airbus chose to develop the latest NEO version of the A320 family, rather than opt for an all-new, lighter weight, latest tech airframe.
The previous 3 generations of the B737 family (original series 100 & 200, second generation series 300, 400, 500 and the more recent NG series 600, 700, 800 & 900) have been and continue to be very successful and safe commercial airliners.
The A320 suffered from early crashes that threw Airbus' fly-by-wire control system in serious doubt.
Thankfully there was little loss of life involved.
Airbus got through that period and have gone on to incredible success with this design.
Note that for the entire A320 family, there have been 118 aviation accidents and incidents, including 35 accidents including a hull loss; resulting in a total of 1393 fatalities.