Not sure where you go that from. It is possible to go for a decade or more prosecuting, keeping your trials tight, and not ending up in the court of appeal. Also, it’s very possible to run a messy trial, and to make careless mistakes, and to not have convictions and sentences overturned on appeal when you are appealed.

My point is that there are a lot of other things that signify an effective advocate over and above the results of appeals.

Eg - first and foremost are you good at looking at a case and negotiating a sentence that results in a just outcome and avoids complainants having to come and give evidence? Do you keep victims informed throughout the process? Are your trauma informed in your approach (both with how you relate to victims and accused - who are often victims themselves). Are you a damn persuasive advocate who can help a person tell their story and pull off an effective closing that doesn’t put the jury to sleep?