Going to Mars would contribute exactly nothing to the survival of humanity, because everybody on Mars would remain absolutely dependent upon frequent shipments from Earth.

Any attempted Mars colony would die out not long after the last shipment, as materials necessary to its continued survival remain unobtainable there.

Furthermore, Starship is anyway wholly inadequate to establish a continued presence on Mars. If it works fully l as well as promised, it might suffice to maintain a Lunar outpost.

Anyone who hopes to establish a sustainable presence off-Earth must look to O'Neill Cans.