I agree with you on the whole. It either needs to be more on the bitter, boozier side or more sour. Now it sits a bit awkwardly inbetween, quite sweet and a bit thin. The flavors are good though. When I made this one I ended up adding some lime, which made it into a pleasant sour style cocktail. Quite a change from the original, but much more enjoyable and balanced. Might try stirring it next time, skipping the simple and increasing the campari.