Will humans ever really be able to get further into space than just Mars?

Answer

You’re right that that carelessness is exaggerated optimism at best. And also that exposure to radiation poses dangers. The development of an effective strategy to minimize the harmful effects of this radiation is an important precondition for ever starting the journey to Mars. But if such a strategy exists for Mars, it can also be used to travel further.

The next planet, Jupiter, is a long way away. The long journey is still too big an obstacle to fly there, but never say never. If unmanned crafts to Jupiter’s satellites confirm that there is a lot of liquid water there, and if necessary find evidence of “advanced organic chemistry,” the motivation to go there will grow. That this would still happen this century does not seem very likely to me, but there will be many more centuries after ours.

Other not unrealistic targets are the minor planets between Mars and Jupiter. And there are hundreds of thousands of them. If you look at NASA’s current strategy, drawn up by Obama’s employees, it is not even unlikely that a small planet will be landed before taking the step to Mars. After all, it’s a little easier to land on a small planet.