For me, a pure black background is the enemy; because macOS doesn't have window borders, only shadows, it's necessary to have some contrast to differentiate between the edges of windows with dark content or dark-themed windows and the background.
In that case, a good wallpaper is just as functional as a plain background, if not more; I usually pick my wallpapers based on contrast with my typically-displayed windows and the usual colours of their content.
Besides which, functionality and aesthetics aren't mutually exclusive.
In that case, a good wallpaper is just as functional as a plain background, if not more; I usually pick my wallpapers based on contrast with my typically-displayed windows and the usual colours of their content.
Besides which, functionality and aesthetics aren't mutually exclusive.