I think graphical fidelity can also be part of usability. Artists always seem to complain about things like waiting for baking lights to finish, shadows having weird artifacts, lighting not appearing naturally and have to resort to using hacks, performance problems preventing the use of certain assets and effects, etc. An overall better renderer would remove lot of the pain from tweaking your art to fit the quirks of the engine. For example, things like SDF-based global illumination would be a godsend to those making outdoor scenes.
