Nobody speaks of restaurant discoverability or beer discoverability or shoe discoverability. That's because nobody would lend the money for a shoe factory, brewery equipment, or a restaurant build-out without seeing a plan for reaching the prospective customers and making them aware of the product. For some reason, people think mobile app business plans don't need this.
That myth may be created by the lucky few who turn out not to need it. They got "discovered" like a starlet at a soda fountain. The app market managers decided to feature that app, or a widely read blogger stumbled upon it. But planning on that is like planning on winning the capital for your next app with a lottery ticket.
If your business plan can't support end-user marketing, you may need to decide you are not writing your app with financial goals in mind, or you need a solid alternative marketing plan and put the effort in to executing that with the same dedication you put in to writing the app.
Tl;dr: Mobile app markets are not a way to get around the cost and effort of properly launching a product.