Also there is some water on the moon so you can make rocket fuel, though how much exactly remains an open question
Questionable.
> but it's so thin you still have to land propulsively using rockets
You have to do the same on earth. Starship sized vehicles have to land on earth propulsively too.
Sure, you can do somewhat larger payloads to Orbit without engines but for large things you need to have real engines.
> You definitely need to sacrifice less spacecraft mass to land on the moon
On the moon you can't aerobrake, that is far worse.
> Also there is some water on the moon so you can make rocket fuel, though how much exactly remains an open question
There is a huge difference. Water on the moon has to be mined from permanently shadowed craters. The water is frozen and incredibly hard, its more like mining stone on earth.
On Mars there are places where you can literally land, drill down and make yourself an underground lake pretty easily. Or land basically right on an ice sheet.
On the moon you need to figure out how to get energy down into the crater, you need sophisticated mining equipment, all that equipment needs to handle incredibly low temperatures.
Mars comparatively is not so far away from earth in terms of temperature for your equipment.
In summation, in-situ for rocket fuel/water is far, far easier on Mars.
Ice is 0.5 Mpa stong in the freezer and 2 Mpa at absolute zero.
Thats tensile strenght of chalk and limestone - you can get that with a shovel. Tensile strength of rock is measured in Hundreds of MPA.
The smallest, wimpiest digger you can find can handle it.
So you need to create excavator that operate inside a creator that can operate at extrem temperatures.
On Mars you can literally do what we already do at the South Pole, drill a hole and make it warm.
Its multiple orders of magnitude easier.
https://everydayastronaut.com/raptor-engine/ (scroll down to the text immediately above the RP1/Methane/Hydrogen chart)