You have to trust the organization, same as always. If your bank/credit union doesn't use https in their app, they probably don't have a secure infrastructure period.
If the organization you're dealing with is incompetent, it doesn't matter if you communicate with https, carrier pigeon, or face-to-face. They'll still leave things open at some point and you'll get screwed.
And, as heinrichf points out, you can MITM and name-and-shame individual apps if you're technical.
