How bad are conditions on Mars if the rovers we have sent there are still functioning?

The absence of any discernible magnetosphere and the planet's atmosphere pose the greatest risks.

The atmosphere is also so thin that you couldn't really breathe anyway. There would be a pressure gradient forcing all gas out of your lung including any water vapor that would have to form since the space in your lungs would have zero humidity. Essentially you would dry out. This also has no effect on a rover. The first one is pretty obvious—humans cannot breathe there because there is almost no oxygen.

In the second, solar winds and cosmic rays are discussed. On Earth, we are protected from both by a strong magnetosphere; however, on Mars, where the magnetosphere is much smaller, high energy solar particles and even more dangerous cosmic rays (high energy protons from outside the solar system) can bombard the surface, posing a serious risk to human health (imagine getting several xrays every day).

The conditions on Mars are harsh but manageable for robotic exploration. The rovers sent to Mars are designed to withstand the extreme cold, radiation, dust storms, and other environmental challenges. While these conditions can degrade the rovers over time, they are built with robust engineering and redundancy to ensure longevity and functionality. The fact that the rovers are still operational demonstrates the success of their design and engineering.