If eating a "good balanced diet" were easy/normal, we'd have close to zero disease. Supplements are definitely a way to get as close as possible to balance when day to day food intake is chaotic.
there is no reason to think a good diet will prevent disease, nor that supplements will help in most cases. Good diet will prevent some disease, but disease is natural in the environment and good diet is mostly your immune system has what it needs to fight it off after you get it.
ErikCorry, bluGill and others like them get people killed with their exceedingly harmful assertions. It is pointless to argue with them since they're here to spread harm, also probably working for big pharma. The best that one can do is ask the reader to find the evidence for themselves.