I had a thought about this dilemma, and based on some of the options families have, I wonder how prevalent very-large pantries and fridges are contributing to some of the difficulties. Is there too much variety going on? I have a philosophy that if something edible is present in the home, then it is food and can be eaten at any time. While some of our limited choices involve a cook-time, most often I pre-cook a few items, like garbanzo beans, and then they can be quick-warmed with hot water for a snack.
We live in a very small space, and have an RV fridge, so we don't have the variety of options that I suppose most families do. We keep one kind of cereal for DD, oatmeal for me, and then cans of tuna for lunch, and pick up dinners as we travel for a couple days at a time. We usually have a few kinds of fruits and then some kind of frozen thing (blended banana and blueberry pops, for example) in the freezer. One thing we absolutely DO NOT do, is keep what we call "not-food" in the house. This doesn't mean we never have a snack cake or some kind of pasta, but we don't "carry" it. We have a picture menu of all the foods (real foods) we like so that DD can look and see what kinds of things she'd like to eat at the same time (brussels sprouts, pears, and spinach with an entire pineapple was her last concoction).
I'm a fan of listening to our bodies, so when dd seemed to eat kale like it was her last meal (for weeks) I indulged. Of course! There might be a good reason her body is seeking heads of kale a day....who am I to tell her it's time to eat acorn squash just because that's what I made up?
I think a lot of times parents are frustrated when kids are saying "I don't like your healthy stuff....I want what's in the snack cupboard", and then we feel pretty bad about deeming those chem-foods "okay" only during certain times of the day or only in moderation, and we might even feel guilty that we have the junk around and have to say "no" so often. If a food can't be eaten at any time of the day and as much as we want, then it's probably "not-food". I know.....some kids can't do a mess of fruit before bed and the like, but on average I think the conflict stems from variety and having oh-so-tasty options within 10 feet.
We have a lot of fun doing "color night" and the like (where all the dinner food is orange, for example), or rainbow night....but blue is a tough one to find in the real-food realm. I think if kids have a say in what's for dinner, they are more likely to be on-board, and when the selection is narrow (such as--only the produce section), the choices are much easier. I think sometimes we're also like Jack Sprat and his wife....dd likes the mushy part of tomatoes, and I like the firmer parts...but we rarely cross over. If I gave her something with crispy tomatoes, she'd likely shove it aside (but I could give her the slop and she'd love it), but if she wanted me to make a dinner that was "all" sloppy tomatoes, I'd be the one hitting the fridge for something different for myself.
I had to do a lot of re-learning with how to make meals after being raised in the midwestern "hot-dish" realm and had to break free of "main dish, side 1 and side 2", so we have what other folks would call quite bizarre meals at times. It's healthy and tasty, though, mostly. The 5 year old says so. Maybe the flexibility we have fits with the odd meals too....We're also okay with mono meals.....strawberries for lunch is awesome.