To be honest, yes, I believe the gist of these theories are legitimate. Conspiracy theorists may have exaggerated some details of these claims, but if it comes down to the basics, so to speak, it makes sense. The pharmaceutical and health care business is a BIG business and money is an evil, greedy motivator.
The gist of the theory is that big corporations operate for sinister purposes and against the public good, and that they conceal effective treatments, or even cause and worsen a wide range of diseases for the only purpose of profitability. Specific variations of the conspiracy theory have included the claim that natural alternative remedies to health problems are being suppressed, the claim that drugs for the treatment of HIV/AIDS are ineffective and harmful, the claim that a cure for all cancers has been discovered but hidden from the public.
There have also been claims about the ineffectiveness of Covid-19 vaccines, the one thing that I don’t really believe is true. Nevertheless, in general, when it comes down to business and money, you don’t know what these people are capable of.