Except for vitamin B12 and vitamin D, you're going to get everything you need provided you get most of your calories from a wide variety of fruits, vegetables, and grains. What is not good is to use a supplement to correct for a deficiency (except for vitamin D and vitamin B12) and then think that you've plugged all holes in your diet. The essential vitamins, minerals, amino acids,etc. are just the tip of the iceberg; for optimal health a lot more compounds are needed than can be found on any list of RDAs of vitamins, minerals, amino acids and essential fats.
We need to consider here that science hasn't yet identified all the compounds our bodies need. E.g. celiac patients who's intestines are so damaged that they need to get supplements via IV, only thrive when given whole food extracts. If they only get a mix of the known nutrients they don't do as well. The difference is then due to the likely large number of compounds in whole foods that has yet to be identified as necessary for the human body.
Suppose that 200 years from now scientists will have identified every last compound you need to eat with their RDAs. If there are 1000 items on that list and today we only have an incomplete list of, say, 25 items with their RDAs, then it's obviously impossible to check if a diet is adequate today. However, there is a statistical trick you can use to guess whether a diet is likely to be deficient according to the unknown list of 1000 compounds.
This works by checking if the 25 compounds in a diet are coming from a wide variety of food sources, here you pay attention to how close different plants are related to each other and also the similarities in the entire profile of the 25 compounds. So, two food sources that are rich in calcium should be considered to be more different if they come from different plants that have different profiles for the other compounds.
Suppose that your diet is not so optimal according to the above criterion, a few of the 25 compounds only come from 3 reasonably independent sources. Then it's a forgone conclusion that your diet will lack many of the 1000 compounds of the unknown list. If you put the compound that comes from the largest number of independent sources on top and below that the compound that comes from the next larger number and so on, then item number 25 of the old list will appear somewhere at the bottom of the new list, but it's likely not going to be the last item of the new list. So, it's quite likely that you are missing quite a few nutrients that are necessary for optimal health.
An effective way to boost the quantity of nutrient intake is to eliminate all sources of empty calories like refined sugars and fats and to get all your calories and essential fats from whole food sources. So, no cooking oil should be used, one should instead eat nuts and seeds. Also, by exercising a lot one can increase the calorie requirement thereby boosting the nutrient intake.