Complete Engine Failure
"Imagine that a company created a certain kind of jet, and before the first test flight they hire an outside engineering company to do an evaluation to see if it is airworthy. Imagine that the official independent engineering report details a number of trivial or ancillary problems (an indicator light here or there was not working properly, etc.) yet fails to identify the biggest, most important thing: complete engine failure. The company wants to know if the plane will fulfill its ultimate purpose; it would not be a very good analysis to ignore the most obvious sign that the plane isn’t going to fly.
Likewise, Paul is examining humanity’s failure in its ultimate purpose of being fruitful and multiplying; and the sexual dysfunction homosexuality represents is sort of like “engine failure.” There is literally no fruit from a same-sex union. Humanity literally cannot flourish if such practices are normative. It would mean literal extinction. Homosexuality represents “engine failure,” the most extreme illustration of futility at his disposal. But Paul doesn’t leave the indicator lights out, either, which is why he gives a lengthy list of sins."