While it takes less time to render an image due to newer and better technology, it takes time to set up the environment, the lightning, the poses, the way how the assets are attached to a character (eg. clothes, hair etc).
However, it doesn’t take that much time either. The biggest problem is the artist’s mindset and their goal to create perfect images. They will spend hours on small details, which only a handful of people will notice, while the majority of people will skip it to reach the next sex animation.