When you check Appstore, you see many nicely designed apps, with many active users. Behind those few apps visible of the Appstore, there are hundreds of thousand of other apps, almost invisible to the users. You may come across them when you are searching for something (maybe for your idea for an app).
In general 80% of the app can be completed with only 20% of the effort, but the remaining 20% is making the difference. Many developers are not being determined to complete the app to the end and release the app just to tick the task.
As most of the tasks, many details should be taken care for mobile apps; like the sounds, the colors / graphics, the animations, the onboarding process, steps to take the user to purchase or keep the interest of the users live. Besides these, there are tasks like beta tests with real users, getting feedbacks and fine-tuning the app, or marketing issues to be able to come out of the app mess in the store.
It’s not a short journey, but the last mile is making the difference. Don’t release the app with a working proof of concept of your great idea.