I agree.. I do think we're becoming less physically fit/resilient as a result of modern medicine. The strong and the weak both survive. However, now that we are no longer being selected based on physical fitness, people like Stephen Hawking get to survive, who would not have lasted 1 second in the jungle or 1 year in the dark ages in his current state. I'm hoping our gradual loss of fitness and natural survivability is outweighed by the occasional Stephen Hawkings of world, who should not have survived, but are making great contributions to mankind because they're alive. And then one day, when we can code out the weaknesses out of our genes, it will all be a moot point.
That is, if don't get over-run by the Idiocracy first.. I would say the best evolved "class" of humans for the current environment on Earth (with welfare, etc), is one that can reproduce rapidly and live off of the productivity of others. Maybe somebody needs to set up a "Foundation" somewhere in Antarctica, to protect our advances/knowledge throughout a possible idoicracy/dark-ages (also useful as a refuge against Tripod attacks..)