I disagree with the idea that usefulness is not truth. More specifically, I disagree with the idea that there's anything else you could really call truth.

Anything that you can actually test can be useful, so you if it isn't useful, you can't possibly figure it out. If there is truth out there that isn't useful, we'll never know what it is. You may understand every useful thing about chocolate, but any other aspect about it you have absolutely no understanding of whatsoever.

In short, by your definition of truth, you are always wrong.