Yeah, I'll believe Mars colonization makes sense once the much closer and more hospitable environments of interior Antarctica and the ocean floor are settled.
Ocean floor is a different kind of problem, and Antarctica (and Greenland) have settlements.
But for similar reasons, I think we should aim for the Moon before Mars: closer, so when (and it is "when" not "if") something goes fatally wrong, it will be easier to get help.
That said, if Starship delivers on Musk's vision, we'll probably get both.
1. killed literally, not metaphorically, everything
2. and literally boiled off all the oceans, rivers, and lakes, top the bottom
3. and strip mined literally, not metaphorically, everywhere to a depth of 3,000 km
4. and removed almost everything from the atmosphere except the current level of CO2/m^3