What makes a tower-defense loss useful rather than frustrating?

The best tower-defense losses seem to tell you exactly which decision failed: a route leaked because the damage was committed too early, a support tower sat out of range, or the economy delayed a needed upgrade. A loss is much harder to learn from when the game hides its targeting, pathing, or why a wave suddenly overwhelmed your build.

Which game gives you the clearest explanation of why a defense failed, and what information does it show?