I think the biggest difference between building a general intelligence and other engineering problems is that in the latter, the target function is well-defined

I think the biggest difference between building a general intelligence and other engineering problems is that in the latter, the target function is well-defined. With planes, anything that is able to fly safely goes. Nuclear reactors, anything that generates electricity. But with intelligence... What does it need to do, exactly? The 'moving goalpost' is moving because we have no idea where it should be. We're building AI blindfolded. I don't think we're currently solving the problem, simply because we don't know what the problem is.