Why are we talking about terraforming Mars? Mars does not have high enough gravity to hold a fucking atmosphere long term. That’s just it. It is not a candidate.
Venus, on the other hand, is capable of being terraformed. It has high enough gravity to contain a human-friendly atmo one day. That’s where we should be looking. Also, Venus is a lot closer than Mars.
However, neither of them has much of a magnetosphere which means humans as configured now get lots of cancer and do undesirable things like die after a few years. So…need better humans and better tech before any of this ever happens on any planet.