That seems to be common conception that people have these days, but many diseases remain largely unfixable, even if some useful improvements can be made through medical treatments.
I think that conception probably arises from people's experience with technology: when there is a technological problem, like for example a computer system failure, usually we are able to identify and then fix the problem, and get the system working normally again. We see this happening all the time, all around us. If our Internet connection goes down, for example, we phone up technical support at our ISP, and they soon sort the problem out.
So that perhaps makes people think they can do the same with the "biochemical technology" of the body, when there is a bodily failure that leads to disease. We may think it is just a case of phoning up technical support, and our bodily malfunctions can be quickly corrected
But unfortunately, with the body it seems that it's not so easy to open up a few "control panels" or "configuration files," change some settings, reboot the system, and thereby resolve the problem. Maybe we will be able to do this in 200 years time, but at present, our ability to fix computer technology malfunctions far outstrips our ability to resolve malfunctions the body. I am sure though as medical technology advances, we will be able to fix lots more diseases.
In 200 years, if you develop ME/CFS, maybe your doctor will say, OK, no problem, we'll have that fixed by tomorrow: we'll just do an HPA axis reboot, we'll delete your adaptive immune system configuration file which has become corrupted with autoimmune data items, and we'll run a full body antiviral laser scan to remove any viral infections. That should get you back on your feet in no time.