Anyone who extols the idea that 'proper training' prevents people from making mistakes, ever, should be immediately fired, preferably in a ballistic manner.
Human beings have this natural tendency to screw up! Sometimes we do so cataclysmically! And one of the benefits of diversity and inclusion is that when one person screws up, we don't just mill about in a homogeneous herd, someone has the ability to recognize the fault and the skills to fix it.
Meanwhile, Boeing execs who can't see past 'Money == Good' are making unilateral decisions and getting people killed through their blinkered incompetence.