Who is the gatekeeper?
Finally the captain should be really responsible guardian of flight safety. My assessment is that this task is sometimes more symbolic than pro-active. There may be instances where results are beyond the capability for the captain and crew to control. In such cases it seems somewhat accepted that given some circumstances, including training standards and seriousness of major faults, loss of life is more likely than not.
Multiple instances of control difficulties on a previous flight of 737 aircraft should have prevented further flights. Captains should have taken responsibility to help ensure non-acceptance of further flight without identification of very serious safety problems. If the next crew is accessible after landing a verbal warning should accompany the detailed technical log report. Take it a step further. Have a list of mobile phone numbers of other company captains on your aircraft type. No excuse for failure to share known risk.
On any aircraft where emergency procedure calls for LAND ASAP, I seriously wonder if crews have spent a rainy afternoon at home considering the logic of their actual response to such a requirement. For instance, consider a cargo compartment fire warning with some evidence indicating the possibility that the warning is genuine and continuing, following smoke and fire procedures. In 40 years of flying significant aircraft, I never heard anyone else discuss the actual flight procedure to be followed or practice it in a sim. I find it difficult to believe that such discussions are too theoretical. Maybe we are not comfortable enough to discuss such things with other crew members.
My actual experience with a seriously damaged aircraft indicated other crews belief in the status quo and unwarranted trust in the safety culture of their airline.