If Starship can get reusable, zero-disposable flight working, and on-orbit refueling, all of those issues become quite surmountable. Mass to Mars (or the Moon) ceases to be "what's the most we can fling in a single launch", and the flight can be shorter if you can depart Earth orbit with a lot more fuel. I can't find numbers for the current iteration, but they were batting around 90-110 day transits with the older ITS proposal.
You start talking about being able to build propellant depots in Earth orbit, build Aldrin cyclers, send large amounts of supplies (or even a whole station on the slow, efficient route) in advance to Mars, etc.
Mars landing of objects is now a TRL9 problem that has been solved already, and the science has moved forward greatly [1]
Recent rover landings happened at what, < 1 M/S ? which is well within the capacity of the human body.
Considering that Mars atmosphere is substantially thinner, and gravity there much weaker, landing there would be different from Earth anyways.
We are not currently employing any of the more cost efficient methods of getting things to orbit in the first place, for large scale missions of epic size, nor are we currently employing the most efficient propulsion types.
The way I see it, the biggest problem is not one actually being discussed which are the longterm effects on the human body of living on a planet without a protective atmosphere, and protective magnetic field [2]. If getting mass to space becomes less of a financial constraint due to more efficient launch mechanisms, then, shielding would much less of an issue because mass in space would be cheaper [3]
I think that much of these problems come down to the huge capital cost, and unsolved problems around low cost launches; the novel technologies that need to be developed & turned into a new space launch system, and no, i am not talking about traditional rockets.
There’s no problem with landing. The weight limitations you mention are entirely a factor if the current “it has to all fit in one rocket launch” limitation.
You start talking about being able to build propellant depots in Earth orbit, build Aldrin cyclers, send large amounts of supplies (or even a whole station on the slow, efficient route) in advance to Mars, etc.