On what pad are you going to land the rocket? You've got to at least level the ground and clear it of debris before a landing. That's gonna take some big construction equipment, even in 0.4G, likely not with a human anywhere near. Likely, you'll need to pour something akin to concrete for the pad, which is not an easy job for a suited up human without any real rad protection. Robots are going to be a major part of any Mars mission as Mars is not a great place to be outside and doing skilled labor.