It took me about 20 years of normal employee/contractor office work alongside creating a side project every few years, to eventually find the side project that would take off.
In the end it was a weekend hack to make something simpler that turned into an app release, which a year or so after that turned into a business.
Sometimes people have a great idea, build it and feel entitled to success with it, but it's largely about relevant eyeballs. If enough relevant eyeballs find your thing and use/buy it then it's a success. It's quite easy to launch something that gets lots of views on launch, but there has to be a reason to come back (sticky apps/content).
I've also built several things that could have been good but I lost interest and ironically the thing I work on now is arguably one of the most boring topics conceivable, but perhaps that's why few people do it well.