Nobody cares about an “app” in the abstract except for the hustle cosplayers on Product Hunt. People do care about an app that does something in particular. If it is for doctors present at a conference on healthcare. If is for cross country skiers then find channels that reach those people. If it has a remarkable technology under the hood find people who are into that.
Generically you need to have at least one persona of somebody who would find the app useful.