The main sign of a properly developed web application design is the user response. If your platform is gaining popularity and attracting your target audience, then the direction is right. Hence, it means that the app is:
attractive;
convenient;
adaptive.
It is also possible to track user comments, which are a treasure trove of useful information for developers. Users are extremely honest and can give valuable recommendations for further edits. Overall, app web design solves the major problems of users and affects the usability.