Yeah, this insistence that any group or society that can't overcome every problem on their own without hiring outside help is incompetent and will die soon anyways is pretty bizarre.

Others have made the rest of the points that I've wanted to make already, but this one I just find very strange. It's both such a common plot and a relatively regular occurance in real life that I just don't understand it as an argument. It's rarely even "hire adventurers or die" for the hirers, typically its just "hire adventurers or life is gonna suck".