Why do some people think we have ~0% chance of success?

The main reason

One way of describing this is that alignment has a logistic success curve. Any proposed solution increases the chance of success only proportional to the original chance. If one is near a tail end of a logistic curve, then moving slightly along the curve has almost no effect on the outcome. For example, if something started out as a million to one odds against something happening, even making it a thousand times more likely gives you less then 1% chance of it happening