Lots of Unity games are what Flash games used to be as well, promotional games, advergames and other things that are part of a larger campaign or system that isn't one off. Most people making money with Unity are building games for shows, promotions, events and others that are marketing mostly.
You can still make money with indie games but more in terms of certain categories or niches.
To make it in games today it is quantity of quality, both are needed.
Unity is making that harder by doing breaking changes waaayy too often. They are making it harder for the smaller/medium game studios with all this technical debt offloaded.
Game development is like any other art form, be prepared to jump from failure to failure and one day one might hit gold, or maybe not.