Discoverability is terrible. For this specific app, it doesn't matter as much, since the majority of our users will already know our service, so we can tell them how to look for the app (which is in itself bad UX). For potential new users, they need to learn about the app somehow, so we need to make an extra marketing effort.

For apps not tied to an existing web property (I'm planning to do some games on my own, for example), you need an effective marketing channel, even if it's just word of mouth. No one is going to just come up with some search terms and find your app.