The best advice is actually very simple.
We can get complex about how we get specific vitamins, too much sugar, too little this or that - but most people can go on a few very basic guidelines:
Focus on protein, fiber, and fat. A well balanced meal will generally have a source of all three. Or at least 2
adult men should aim for 35g fiber, adult women 25g
keep sugar to 10% of your daily calories a day, on average. If you eat 2000 cal a day, you’d want to keep your intake of sugar to 50g or less
Part of the reason why it’s hard to know exactly how much of each micronutrient we need is because that can be very specific to the needs of the individual, like health issues someone may have or what someone might be at risk for. It’s not typically the case that someone has to worry about nutrient deficiencies if they are following very basic guidelines
For example, if someone is eating enough fiber, it’s not likely that they are not getting enough sat, vitamin c, given how many vegetables and fiber sources have vitamin c. But at the same time, someone can have a deficiency in a certain vitamin that could be related to a health issue, nor necessarily caused by the way that person eats. It gets very specific