No. This is a result of thinking of natural selection as working towards an "absolute" better and away from an "absolute" weaker, as opposed to pushing in directions that are entirely defined by the situation.

Natural selection is this: in populations that make copies of themselves, and have mistakes in their copies, those mistakes that better fit the situation the copies find themselves in are more likely to be represented in that population later down the line.

Note that I didn't say, at any point, the phrase "SuRvIVaL oF ThE FiTtEsT." Those four words have done great harm in creating a perception that there's some absolute understanding of what's permanently, definitely, forever better, and natural selection was pushing us towards that. But no such thing is going on: a human may have been born smarter than everyone alive and with genes allowing them to live forever, but who died as a baby when Pompeii went off - too bad they didn't have lava protection. Evolution is only an observation that, statistically, mutations in reproduction that better fit the scenario a given population is in tend to stick around more than those that don't - and guess what? That's still happening, even to humans - it's just that with medical science, we're gaining more control of the scenario our population exists in.

Now, can we do things with medical science - or science in general - that hurts people? Sure, there's plenty of class action lawsuits where people sued because someone claimed their medicine was good and it turned out to be bad. But if you're asking "are we losing out on some 'absolute better' because we gained more control of the world we reproduce in," no, there is no "absolute" better. There's only "what's helpful in the current situation," and medicine lets us change the situation instead being forced to deal with a given situation, dying, and hoping one of our sibling mutated copies can cope.