"A Mistake For You to Accept Promotion"

[DataLoreSpock]

Kirk was probably competent at other jobs, but excellent at starship command.

That is true.
You can be the best at one thing and be the worst at another.

 

[pengbuzz]

Yes; Kirk's best was starship command, and he was at his best when in command of a starship.

 

[Anji]

The only other truer statement ever said in the franchise was: "Jim Kirk was many things but he was never a Boy Scout."