There is usually no such thing as "safe" or "not safe". It's more like "X% chance to happen". X might be really, really small, but not zero. Usually you can make X arbitrarily small, but the amount of money needed grows non-linearly. Do you pay 10x the price of an aircraft to reduce the chances a problem so that it goes from happening once every 100 years to once every 1000 years?
Who should make the decision whether an airplane is "safe enough"? Should it be the buyer who wants the safest plane? If you did that then rich airlines could keep out new competition by specifying safety features that make airplanes more expensive than they need to be. Should it be the country where the airline is based? But different airlines are based in different countries. Should there be options so that one country can specify higher standards than others?
Basically, that's how you get where we are I think. I'm not sure how you avoid that.