> unlike earth there's no magnetic field or enough atmosphere on Mars to deflect them

These are solvable with known methods.

They make the whole thing rather less romantic.

If you're going to the trouble of e.g. burying your base under regolith or wrapping a planet in a big coil and lots of PV to make an artificial magnetic field, it very quickly becomes apparent that for essentially all possible disasters short of "oops we made a black hole and it caused a magnitude 15 earthquake and all the crust everywhere liquified and mixed with all the water so even ocean bases weren't safe", it's much, much easier to survive disasters on Earth without actually leaving Earth, than to go to Mars and have a normal day.

If someone made a robot factory that went mad and converted all the nitrogen in our atmosphere into ammonia (killing all the plants that no longer had access to the atmospheric nitrogen), while also producing enough smog to halve how much sunlight we got, and dumped a lot of endocrine disruptors into our water cycle, the top of Mount Everest and the Sahara desert would each still be much more hospitable than Mars is today.