I looked up the screenshots. The app looks like the most trivial possible UI for basic public key cryptography. Just a basic list of your/other people's keys (pretty much a contact list) and some ways to acquire them.

SSH keys if used in place of GPG would have almost the same UI. It's not the problem of GPG, but of the underlying concepts.

You don't need to be deep into cryptography, just understand some basic concepts from the wikipedia article, or whatnot.