> An engineer [] went to a credentialed school and passed a bunch of test and is allowed to sign documents that state "this thing, if built this way, won't collapse and kill people."
Ahhh - that old craptacular definition. You completely ignore mechanical engineers, chemical engineers, electrical & electronics engineers. Not all engineers make bridges.
Secondly, the implied cause and effect even within civil engineering is a fantasy. Signatures on documents by credentialed engineers doesn't prevent disasters as you noted: Bridges fall down, buildings burn. Read the engineering reports on civil engineering disasters, and look at the consequences for the engineers involved.
You do some handwaving about organizational/process problems, but actually that is the key to safe engineering. Organisations deliver engineering projects and they do it across jurisdictional borders using insurance and liability and with a variety of other means that work: "signatures don't prevent disasters".
Lockheed Martin's skunk-works and SpaceX are real engineering. Any good definition of engineering needs to encompass an extremely wide variety of activities.
Engineering is compromise. I have no love for Musk but him saying build that actuator for less than $5k is actually true engineering: https://news.ycombinator.com/item?id=39085892
I would like to know the psychology behind why people wish to believe credentialed signatures are so powerful? Maybe a cross between two concepts #1: "that individual engineers run the world" and #2: "that retributive punishment of individuals works as a deterrent". I think concept #1 comes from the egotist idea of most engineer-types that we are the center of everything (I need a whole article to explain the concept). I think concept #2 is related to beliefs about the value of incarceration and also punishment beliefs derived from religion (especially in the USA where prisons are not fixing problems?).
Edit: issue #3: the idea that we should make rules about what words mean. It takes a certain worldview to think words should be defined rather than evolve (or worse that words should be part of a justice system)