We have the technology to deliver payloads to Mars. We have the know-how to live there, produce rocket fuel for the return trip literally out of thin Martian air (thereby reducing the weight of our launch considerably) Why are we not focusing on this?
Mars is key to so many things. It can inspire an entire generation of new scientists in a way that the ISS simply does not. The construction of the necessary mission hardware will stimulate our economy and create high paying jobs. However, perhaps the greatest contribution would be the ability of our explorers to search for traces of ancient Martian life, or even better, existing subterranean life.
So let us do this thing. Not because it is easy, but because it is hard. And also, because there is so very much to gain.