The main issues with it in CDDA is its near impossible to tell what you are lacking and that most foods dont have any of the vitamins or whatever. It would be less of an issue in Rimworld, tho it would still be a pain in the ass and would need a few foods to be added lest the veggie-munchers all die from lack of protein thanks to lack of plants containing it.
It would also give a good reason for finally letting us make tea from roses and the like. Wonderful source of vitamin C, rosehips.
From my memory of modding my own work (not public), it's fairly complex-ily simple. There are several values (less than 5) which go "Nutrition", and Health in general--vitamins help by being a timer of sorts or value adjustment into the positives and health fluctuates around a certain minor range. Eating 'unhealthy' foods like junkfood or otherwise brings that health value down. Nutrition is just a term to help you get in touch with it more.
So yeah.
Problem is, CCDA does generate it very well. You won't find good stuff unless you up your survival skill or get good loots.
...Just like in a post-apocalyptic scenario exactly.
It was never bad enough for me as I dared go and forage--it also somewhat challenges your time management which is what I loved there. (Y'know, after I got a watch...but the basic vanilla default is good enough)
It just looks difficult because of how variant RL impressions are. In CCDA, it's a simple but seemingly complex impression.