Failsafe is extremely difficult to imagine without numbers relating to probabilities. Tis true that some parts of a machine such as wing spars are designed with lots of margin to long life with inspections and consideration of storm encounters, damage etc. But most parts can't meet this same requirement and still maintain the total aircraft weight low enough to get off the ground.
Instead mitigation against the consequences of their failing is considered in a probalistic hazard environment.
Things like redundancy/duplication, shielding etc. are considered at the aircraft system level.
If you want to get into this kind of discussion you have to be prepared to work with probabilities and even with that you are still left with some chance of what happened in this event.
We are waiting for the investigation to reveal the causal chain so that one or two of the links can be altered to minimize a future event. Don't for minute believe you can achieve zero engine disk failures, but you can minimize some specific identified cause based on new knowledge.
The message is always the reaction to what we learn and not blame.