The problem with most big button phones is the lack of a decent screen. The Doro 6520 is a clamshell design, with a few bells and whistles for the disabled such as an assistance key. Though the keys aren’t particularly large, they are widely separated. It’s really a choice of one or the other- big keys and small screen, or smalller keys and a bigger screen with camera.
I’ve never seen a big button phone with a decent screen and camera, but they must exist somewhere, I would have thought.