True enough, good example.
If we keep intervening with treatments of diseases then we will end up having people who WILL start being allergic to some, many then all of those medicines. Nature will keep inventing diseases that will keep being immune to the cures.
One sees that with the ever-changing chamelon-like AIDS virus. They mutate right under the microscope while a medication is being administered to kill them. Amazing things viruses. They can't be killed apparently, only allowed to die natural deaths while the patient manages to survive them.
I imagine that one day in the future there will first be screening for diseases and parents will have to choose to live with them or not. Unfortunately, abortion on demand for the first trimester will still be around.
Then, most probably there will come a time when parents might be able to do corrective gene therapy, perhaps to correct some horrible diseases (Alzheimer, strokes, etc.). That will be good.
There will STILL be diseases acquired by lifestyle. Those will still be subject to the same natural "rules" above, as to the efficacy of an individual's immune system.
Then, I imagine someday parents will be able to choose such things as eye/hair color, then ... other things, such as a disease free baby and perhaps even more esoteric choices.
The best thing would be to inherit or genetically implant the BEST immune system a human can have.
Nature did that already with the likes of those people I mentioned, with NATURALLY ultra-superior immune systems. Then, we interrupted with superior medicine, allowing more and more "inferior" immune systems to survive, thrive and pass along the weaker and weaker genes and immune systems, saving people with medication, implants, transplants and devices.
We COULD go the bionic route too, of course. Then parts would be bought and paid for .... naturally, either by the wealthy, middle class, or GIVEN to the poor, compliments of the tax payer.
Nothing changes, does it?
My personal choice would be to have the naturally superior immune system....and bionic legs, eyes, hearing, teeth and hair. Well, nice skin would be nice to have too. Lol. Can you IMAGINE the genetic mess we WILL get ourselves into? Boggles the mind.