A manned Mars mission is within the grasp of existing technology (and has been for 40 years).

Fusion power isn't.

Mind that I'm not arguing for or against a manned mission to Mars. I don't think it would prove any tremendous benefits, though it would be most decidedly cool. I also believe that permanent or long-term Mars settlements are well beyond present technical capabilities.

But the difference here is political will and financing. Not underlying technical viability.