Why can't that "different approach" be simply painting (realistically) things that don't exist? For example: Pictures of something that existed in the past, b

Why can't that "different approach" be simply painting (realistically) things that don't exist? For example: Pictures of something that existed in the past, but was destroyed. Or someone who died. Or a younger portrait of someone. Pictures that differ from reality, such as putting together two famous buildings that actually exist in different cities, near-equator stuff covered by snow, scenes containing objects with incorrect size... Or impossible structures, like Escher did, only more realistically. Science fiction, fantasy, fairy tales... Painting a "realistic" dragon requires skills, and cannot be replaced by photography. Why don't modern artists show their skills at this?