> Either the option was safety critical, in which case Boeing had no business making it optional

This is the part I was trying to clarify. I don't know Boeing's internal processes, but there certainly could be options that are safety-critical but still optional because they are ranked low enough on the severity/probability/detectability scale.

I agree that it's wrong to blame Lion Air as the consumer. The fault seems to be in Boeing misapplying the risk categorization.