To me the more interesting point is the high risk. Given that someone is using a needlessly complex technology, and given that they can't maintain it themselves, they actually do need someone who can handle the needlessly complex technology. So unless you're brownfielding, the practice isn't unethical. But it can still be high risk -- mainly, I guess, because of the high opportunity cost of coupling your expertise to suboptimal tech.
Thanks for the book rec! Something that moves from Lamport's short, theoretical (but awesome) piece to concrete examples is exactly what I need. Will check it out.