A project goes beyond just the functionality in the sense that there are several things you have to take into account apart from something working as intended at first glance. You just need to look at the tea app leaks to see the results of a purely vibe-coded project with zero thought behind it.
You have to also think about how easy to understand and mantain your project is, as well as the modularity behind it. You also have to take security into account, which is a whole different branch of programming people devote themselves to studying.
Your android calculator app may work, but it has to stand the test of time.