To my mind as potential passenger it comes down to certification . It seems Boeing and the FAA are too cosy- its not unreasonable to delegate some things to the manufacturer because they have resources and expertise but perhaps thatc ulture became too ingrained and everyone got tripped up.
Is the MAX really still a 737 after 50 odd years; 3 engine types, new wings, new tail, vertical and horizontal , undercarriage changes due to engines, fly by wire, all digital flight deck no doubt a lot of structural changes internally to lighten weight - the only things that seem to still be 737 are the flight deck windows. Should the FAA really have accepted the grandfather premise or just told Boeing , especially after the 739 -sorry you are just going to have to call it 797. Its a great engineering feat , up to a point, but as MD found out when they went one step beyond with the MD90 you can go a stretch too far and not just in dimensions,