At the same time, the lesson to be learned is that useful ai can have a utility function which is pretty mundane -- e.g. "find a fast route from point A to point B while minimizing the chances of running off the road or running into any people or objects."

Self-driving cars aren't piloted by AGIs in the first place, let alone dangerous "world-optimization" AGIs.

Similarly, instead of telling AI to "improve human welfare" we can tell it to do things like "find ways to kill cancerous cells while keeping collateral damage to a minimum." The higher level decisions about improving human welfare can be left to the traditional institutions - legislatures, courts, and individual autonomy.

The whole point of Friendly AI is that we want something which is more effective at improving human welfare than our existing institutions. Our existing institutions are, by FAI standards, Unfriendly and destructive. Not existentially destructive, this is true (except on rare occasions like World War II), but neither are they trustworthy when handed, for instance, power over the life-and-death of Earth's ecosystem (which they are currently failing to save, despite our having no other planet to go to).