Humanity isn’t the problem, it’s the 90% (by number) of cells in and on your body which aren’t you. We each carry a vast colony of other life forms, some of which could very well exploit environmental niches on Mars and possibly wipe out the very life forms we want to study.
Where I come from that’s called dumb. YMMV
“Dumb” would be not taking absolute precaution against Martian life, if there is any, getting loose among the crew.
Those precautions would, secondarily, isolate Martian life from us.
Imagine what a DNA/RNA that could survive in that environment would do on Earth!
Doubt if anything good is found but it’s worth a look.
There’s no need for Humans on Mars for several decades. It can be explored by robots up to a point that won’t be reached for quite a while.
Eventually it will be populated, though it’s not very satisfactory.