I'd disagree with aircraft. The modern 737, the NG or the MAX, is a world apart from the plane that first flew in '67. Almost everything except for the seating

I'd disagree with aircraft. The modern 737, the NG or the MAX, is a world apart from the plane that first flew in '67. Almost everything except for the seating configuration has been upgraded or changed on the plane. The type-rating laws also provides Boeing with an incentive to keep the plane just similar enough that a crew can transfer from one class to another without too much training. It's also not Boeing's fault that there's a huge international market for a plane of that size and range. Boeing does have its faults though.