well for one thing we already called it a contrivance.

god from the machine is bad because it's nakedly from the machine. it's low-effort it's not clever. it's non-s equitur

like, taste is subjective or whatever, but our hegemonic culture I think rightly disapproves of a writer solving a plot problem by having somebody show up who had nothing to do with the whole rest of the story or having some random event happen.... unless it's carefully done as a subversion of expectations like having some family drama and then they all die in an earthquake and there's some point being made.