It’s completely ridiculous to think that humans could live on Mars

You're joking, right? The ISS gets everything from Earth, even its water, and they're so bad at self-sustainability that they are not able to wash their own dirty clothes (I shit you not). Oh, and they throw away their feces and only recently were able to grow some lettuce on board. That's the state of the art right now.

We are not making the Earth less inhabitable. More people live on the planet now than ever before. In fact, many really smart people over the years have told us that the planet would never be able to support the current population.

There's an undercurrent in this article that's extremely dour, depressing, and bleak. I take issue with that, but we can save that conversation for another day.

People will visit Mars. In fact, for many decades it looks like tourism will be the prominent industry.

Mars has water. Mars has CO2. We can make a breathable atmosphere and support ourselves, although it looks like living mostly underground is our best option for the foreseeable future. In my mind, what we need is cheap/free energy.

Nuclear batteries look like the best option, at least initially. Also a modular, standardized deployment system where things plug into each other. It'd be good if for a while we equip every piece of gear going to Mars with power and an O2/water generator.

No matter how it plays out it'll be interesting to watch. Too bad it will probably take a long time before we see a sizable population there.

[1] Tourism in Antarctica. https://en.wikipedia.org/wiki/Tourism_in_Antarctica

Triumph of the city/network effect argument: Networking and connectedness into other people and increasingly into computer services around the world provide more intellectual satisfaction than surviving in the desert does. Mass of humanity produces more variety when it clumps together physically. Urbanization on the earth is driven by productivity growth from cities. Immigration to distant colonies could be justified with farmland and resources in pre-industrial society and industrial society. If post-industrial society with deceasing population builds distant colonies, it wastes resources.

After the thrill of interplanetary space travel wears off, Mars may have small outpost for geologists, geochemists etc. I think colonizing moon will be far more likely when technology allows it. You can have access to Earth and communication lag is acceptable. Moon colony may be economically profitable.

Good thing for us all that it isn't an either/or.

Fortunately some people can work on the good and needed. And some people can work on the hard, maybe even the too hard to see at first that it's even possible.