"The whole reason of the existence of the MCAS is to avoid training the pilots to fly the planes without it." That summarizes why the plane did not go through

"The whole reason of the existence of the MCAS is to avoid training the pilots to fly the planes without it." That summarizes why the plane did not go through a new type certification process - avoid costs of pilot training. Boeing instead painted over the differences (larger fans mounted forward) with software to make it feel the same.