I agree. Harry was great at his job and quite intelligent. I think Garret as an actor did nothing to inspire them to do more with his character. If he had, Harry could have evolved much more. If you have someone on your team that's only doing the bare minimum, would you feel compelled to give them more challenging tasks? His range as an actor was mediocre. Comparing him to the rest of the cast, I think he was the least talented IMO. Or maybe he had more talent but never really worked to show it.