I think that's the point Gentar was making, Baldur - even abstract art depends on a solid understanding of realism.
I see your point, and Gentar's, for that matter.
I acknowledge that photorealism is required but reality can be built on more than paper, to understand reality you must observe it. I'm not telling you copying nature is wrong, 'tis a great method for many. Observe that Nature and reality are two completely seperate things.
I have never been good at photorealism. Understanding why a tomato should react to light like that and understanding a head's form(Look up an anatomy book, observe your body's forms) and how and why it reacts to light like that, shaping shadows, the skin you see being the light's reaction to the skin's surface. Train this skill, this understanding, and drawing realistically will be more easier.
Creating reality is as much emotional partaking as it is artistic, therefore the greatest advice I can give one who's just beginning his/her journey are impressionistic base compounds. No copying. Understanding reality, thereby better sensing reality, and making something beautiful.