In time, drier cocktails such as the martini were invented. One could say that the mixed drink had matured. More advanced drinks add more liquors and mixers and play with the proportions. The key is to have a final product which is not too strong, not too weak, not too sweet and not too dry. These also depend on when the drink is being consumed.
Many people enjoy sweet aperitifs before dinner and drier digestifs afterwards.
On the other hand, many times a sweet cocktail is drunk with dessert. The key when mixing drinks is that all ingredients be ice cold. If you can, refrigerate everything, including the glassware. When you use a shaker, fill it half full of ice and add the liquors and mixers. Immediately strain the drink out into the proper glass.