I imagine it would be very difficult. Getting to the moon was all about weight. Getting to Mars with a lander that could carry enough fuel to escape the planet’s gravity for a return trip would presumably mean a larger rocket than the Saturn V. If you aren’t planning to bring back the explorers, I suppose that makes it easier. I’m nobody’s rocket scientist though. :)
The moon has 1/6 the gravity of Earth, but Mars has 38 percent of Earth’s gravity. That seems like a lot of fuel a lander would have to carry to return astronauts to Earth.
Oh yes, very difficult, very expensive, but suppose the next generation antibiotics could only be found there? (As an example of a compelling reason I just made up right here on the spot)...