Can multi vitamins and other supplements entirely make up for a diet which lacks nutrition?

Not really: Good nutrition comes from nutrients in whole foods. With that said, many fruits, vegetables and foods don't necessarily supply the body with all the nutrients that it needs. For example, once a fruit or vegetable is cut from its own nutritious source, the vine or tree, etc, it begins to slowly lose some of its nutrients. This is why taking vitamins and even supplements may not be a bad idea.