Which wartime submarine programs misused scarce resources?

Which World War II submarine design was least useful, or represented resources that would have been better spent elsewhere?

The panel nominates the Type XXI and I-400 programs because their late, costly development offered less value than more proven submarines or an earlier mass deployment.

One answer argues that German resources spent on the Type XXI might have produced more effect by improving and supporting the proven Type VII fleet. The Japanese I-400 class is another candidate: its concept might have mattered if a sizeable force existed before 1941 for coordinated strikes on targets such as the Panama Canal, but arriving late left little time for strategic effect. The lesson is that an advanced design can still be a poor wartime investment when development timing, numbers, and support do not match operational need.