Why British carrier changes did not prove US incompetence

Did the need for British changes show that American carrier design was incompetent?

No; it reflected different combat experience and a deliberate tradeoff between immediate production and design changes.

The British had combat evidence the United States lacked, while American yards were trying to maximize production. Stopping a line to incorporate every improvement imposed a real delivery cost, making the difference one of prioritization under unequal experience rather than incompetence. Once the Bureau of Ships understood the British reasons and compared them with American losses, later production could absorb the changes. Design quality has to be judged alongside combat feedback and production tempo.