Do not build an app to decorate a brochure site, to follow a competitor, or to postpone a website that is already unclear. A phone will not make a vague offer specific.
Wait when the process is still changing every week, when you cannot name the user, or when the team cannot support a store release and the fixes that follow. Those are product problems, and an app will freeze them.
A focused site, or a narrower tool inside the site, is often the honest first step.