If a company cannot be trusted to maintain safety on one particular production line why would you have confidence that the other ones are OK? Not understanding

If a company cannot be trusted to maintain safety on one particular production line why would you have confidence that the other ones are OK? Not understanding that, if I was going to filter out certain trips I'd want to key on "Boeing" rather than "737". Or at least newer models from an organization seemingly in decline. That includes the 747, 777 and 787 according to Kayak. And since plane travel in general is so darn safe, I'd just use it to possibly select one flight over another rather than to rule any out.