The species would not really be much "tougher" if modern medicine had never been developed (well perhaps there might be less allergies but that's not due to evolution).I believe we've broken natural selection. Imagine how tough our species would be if hospitals didn't exist. (Or we'd be extinct).
Modern medicine is relatively new and bacteria and viruses evolve far far faster than we do anyway.
You could probably make the case that without modern medicine conditions like sickle cell anaemia or cystic fibrosis would be rarer in the developed world. (But then what exactly does the "developed world" mean if we are disregarding modern medicine).
Most mental health problems would be completely immune to evolution because they kick in long after individuals reach reproductive age. (and if there were no medicine no one would live that long anyway).
Hospitals reduce the selective pressure against genes that increase the probability of contracting a condition that is treatable, they do not remove that pressure unless modern medicine has reached the point where that condition does not constitute a disadvantage _at all_.However, we have hospitals, medications, urgent care clinics, etc. to care for the weaker and dumber members of our species (along with our emotions such as compassion, generosity, and other bonds).
Fittest is only fit in the context of reproductive fitness, that's all evolution "cares" about, if being thick but strong makes you more likely to reproduce then that's what evolution will favour.survival of the fittest/smartest would
Hospitals have not stopped selection, people still die before they reach reproductive age. Further selection is not limited to death, selection is based on reproductive fitness, obviously dead people can't reproduce but two live people are not necessarily equal.
The phrase "increasing life expectancy past what it should naturally be" has no meaning.So, with the halt of natural selection due to hospitals (increasing life expectancy past what it naturally should be), and the reproduction of flaws, we've also halted evolution.
We haven't halted evolution, we've altered it perhaps but the real reason why evolution is fairly irrelevent for our future development is because technology has rendered it redundant: technological development is orders of magnitude faster than evolutionary change.