The reliance on a phone seems terrible, I would never install a banking application unless sufficiently threatened. I prefer our (Czech) more-or-less direct bank transfers, for which I don't need to leave my web browser.
It should also be noted that in general, Xlib can do a lot more than XCB with a /lot/ less effort and bugs, and has an actual documentation, tutorials, books.
Xlib certainly is quirky, in particular around error handling, though.
I think the most free-minded large models might be the Groks, but just slightly, as they have different biases. In sum, there's strength in diversity.