Very happy to be corrected, but I feel like this is one thing we got right.
We fed DS an iteration of whatever we were having. Meal times were a family affair. This meant our meals were quite simple for a while. Eg. Scrambled egg, brocoli, rice, optional soy sauce (minimal).
We always offered pudding, and pudding was nutritious. Full fat Greek yogurt, a fruit he liked, oats (protein, carbs, vitamins). He loved this, so however little he ate at dinner, he had something with some nutritional content for pud.
We always had a "It's OK to not like it but let's try" mentality. If he rejected something, that's fine. There's always pudding. He surprised us and himself with the things he liked.
Now, he's 8. He eats lentils, curries, herby omelets, chilli, courgette pasta, tofu, fahitas, lots of grown up things. Often a side order of bread helps, with ratios agreed.
Ultimately food is good fuel and good pleasure in our house. I'm very aware that it might just be luck!
School, peer pressure and a love of burgers and pizza has set in. We counter this with veggie burgers and homemade wedges every other week, homemade pizzas. Last Saturday his treat of choice was homemade falafel, salad and halluni wraps.
There's plenty we've cocked up. But DS's relationship with food (so far) isn't one of them.