Have you ever had an unsuccessful project and what did you learn?

A while ago, during my tenure at my previous company, we concentrated on developing an app based on assumptions of user preferences, neglecting early user feedback. As a result, when we eventually launched the app, it lacked crucial features and had a user interface that did not appeal to the intended audience. From this experience, I learned the importance of actively engaging end-users in the development process through surveys, focus groups, and other means. Their valuable feedback can steer product development, ensuring it aligns more closely with their preferences and expectations.