Really? I would think that sign would help everyone who knew how to read, bothered to read, and wanted their car to run. A sign with a simple message like that was enough to fix one national timeclock system that I worked on. "Do not do X before 12:00 Noon unless Y." in English, Spanish, and Polish.
For the people who still messed it up that we found by using heuristics on all of the punch data, we sent reports to their managers that said that they had probably done something wrong. After 3 or 4 cycles of this, the failure rate went from 15-20% to 1-2%.
Unsophisticated users remain unsophisticated users if you systematically remove configuration until the application only does one thing one way, badly.
But, yes, clearly, the goal is removing configuration until the app does one thing well, not badly.
If you know your car runs on gasoline, and you don't know the difference between gasoline and diesel, then you see a sign that says "diesel is not gasoline," you know that diesel is not what you're looking for - even though you still don't know the difference.