The customer/user can't tell the difference between a good working app and a poor working app.

Come on man, this is the whole reason Duolingo was people's favourite language learning app, or people claim they like iPhones over Android phones or Photoshop over Canva. These apps and devices all work, but which one is good or better is a debate. People have preferences; some apps in a category are easier to use than others, and some apps have branding that signals status. Now, those things become more important in differentiating your app than "It does what it is supposed to do". Until now, just getting an app to do what you wanted it to do was a competitive advantage, that's becoming a smaller advantage day by day