The question is this: Do you want to build within a certain set of categories Apple unambiguously supports?
If you're building a to-do app supported by a monthly subscription, there's no shifting foundation there. If you're building a free-to-play game whose in-app purchases consist of "handful of gems," "bag of gems," and "trunk of gems," you have nothing to worry about from App Review.
If you're building something without obvious precedent, however, trying to break new ground in the spirit of tech entrepreneurship – the answer is no longer so clear-cut. And so the App Store has in many ways self-selected developers for "safe" categories over the past decade, and yes, many of these have found great success (even if that half-trillion dollars tends to follow a power law with most of it going to the top earners in each category).
What the App Store is definitively not, however, is conducive to innovation, experimentation, and risk-taking. There are outliers, of course, who have managed to do something novel within the constraints set down by Apple. But the biggest risk you take when building your business on the App Store is not that your product will fail in the market, but that Apple will prevent it from ever reaching the market.