As technology progresses, so does the protection against various illnesses. However, with each advance in modern medicine, evolution loses just a bit more of its ability to weed out weaker individuals from our gene pools. If life were to progress as it is, we would eventually bring the entire process of evolution to a halt by treating genetic mutations and sustaining evolutionarily unfit individuals.
In fact, if things were allowed to progress even further, a new process of de-evolution could potentially occur. In this process, we can assume that the "unfit" individuals alive due to modern technology would supply unfit genes to their progeny, who in turn would spread those unfit genes further and further eventually resulting in a majority of humans having those unfit genes. Quite potentially, these unfit genes could become the predominant gene and wipe out other more traditionally fit genes resulting in a physically inferior human race (think of those sci-fi movies where the technologically advanced aliens have frail and fragile bodies - ie. War of the Worlds, ET, etc.).
How I see it is, there are two paths for an evolutionary species. The first is the scenario I mentioned before (weak anatomy, physiology, and biochemistry with highly advanced technology). The second is a no or limited technology scenario where survival of the fittest results in physically superior individuals (think aliens with special heat seeking eyes or the ability to lift ten times their weight, etc - ie. Alien, Superman, etc.). We as a species have chosen the former. Technology offers us vast possibilities in achieving our individual and special endeavors while the latter is more chance based than anything.
While we have chosen what seems to be the more rational path, I am being honest when I say that I am a bit curious to see how we would have turned out had we let nature take its course. (I mean, it brought us this far didn't it?)