Many of the landers we've already put on Mars are heavier & less tolerant of G forces than a human, so it's clearly not an insurmountable hard limit. They use a

Many of the landers we've already put on Mars are heavier & less tolerant of G forces than a human, so it's clearly not an insurmountable hard limit. They use a combination of parachutes, retro rockets & airbags usually. But you're right that the lander stage has to be a small fraction of the size of the interplanetary stage, & the economics aren't very good. Maybe you'd need to send several Starships to Mars orbit to refuel & support a single one landing &/or returning to Earth -- at least until refueling facilities exist on the surface, & assuming Starship is actually capable of this mission.