Given current diagnostic technologies, correct. I think genetic data and other types of bio data can be used to invent significantly better diagnostic tools that would reduce or eliminate the problems you talk about.

For example, we currently do not have a diagnostic test that can tell the difference between a virus or bacteria so physicians prescribe antibiotics just in case. If we did then we could reduce the use of antibiotics. Genomic sequencing won't help this case specifically, but sequencing at the proteomic or metabolic level may.

Not to mention that the majority of modern pharmaceuticals are focused on treating symptoms instead of causes. Insert argument about sick people being more profitable, etc.