Pushups are a great basic exercise which helps you condition your entire body, not just your chest. While doing a pushup you train your chest, shoulders, arms, even legs and core.
But once you get more advanced, doing pushups becomes relatively easy and you need to start adding resistance, i.e. weight or reps, but you are kind of limited in some way. Adding reps becomes somewhat useless after a while.
About the "muscles dont grow and I lost motivation"-part, whether your muscles grow or not has to do with more than just this exercise. You need enough food, rest and progressive overload to achieve muscle growth. Are you sure you're getting all of the above? And are you doing more than just pushups?