A basic principle of nutrition is that our diet should provide all the nutrients and vitamins we need. If that’s not the case, it is a sign that something is wrong with the diet. That means that, apart from people with special needs (such as my need for Vitamin D, which is not diet-related), in general everyone should be properly nourished by a given diet.
You may or may not need your vitamin pill and supplements. If you are just taking them on your own, you might very well be able to dispense with them. If you are taking them on a doctor’s advice, then consult with the doctor.