That's a very brass statement considering the cornucopia of documented results in online medical journals. Herbs and drugs alike contain active substances, some of which, are more effective than others. Some vitamins may cause parasites to become more resilient, hindering the effects of anthelmintics.
Taking the wrong drug or herb cures nothing. Misdiagnoses cures nothing. An insular mind cures nothing. If your model fails, try another or expand your paradigm.