I don't think that's necessarily the case.
There is much more that we know than just "Vegetables are good" and we know why they're good. Nutrient dense, packed with fiber to slow digestion, includes necessarily vitamins and minerals to not only absorb the nutrients of your food but to also provide you with the micronutrients you need.
That's of course just one example you made. But the problem is where people go to find the right information. Don't watch instagrammers and don't look at the latest "super foods" where the benefits might only be marginal, albeit hardly palatable.
Having studied nutrition and human movement in first year University, my recommendation is for people to actually buy a first year Uni textbook on nutrition and understand what is in your food, what energy systems are, what macro (carbs, fats, proteins), micro (vitamins, minerals) are and how they impact your body. Then you can go and make more informed decisions about what you eat without someone necessarily telling you. You'll know that sugar isn't bad for you, but copious amounts of simple carbs like Mars bars are especially if you're not exercising.
Top level Athletes and body builders are the way they are because of how they train and but largely how and what they eat. If we didn't know that much about nutrition we wouldn't have many world class athletes. As the saying goes, you can't outrun a bad diet and that's true.
If you could afford a sports dietitian, I guarantee they'll know what you should be eating in combination with exercise to be healthy.
A big problem with the Nutrition industry is that its easy to make big positive leaps in what you eat, without it being a bowl of kale and beetroot. The challenge is people's ability to be able to plan and cook properly between their busy lives where nutritionally simple foods are more readily available. Additionally, in today's world of many of us sitting in offices all day, you cannot live a healthy life purely based on what you eat, you need to move your body and exercise as well.