That’s a long way down the road, though. Before that, we need to develop a huge amount of infrastructure in space, and doing that will be extremely expensive so long as we have to fight Earth’s gravity well to do so (even accounting for things like cheap reusable rockets).
Either the moon or mars could serve as the “stepping stone”, but I think Mars is better situated for that due to having a wider variety of raw resources available and being overall less harsh than the moon while also having a dramatically weaker gravity well and practically nonexistent (aerodynamically speaking) atmosphere that would allow launching of vastly larger and oddly shaped crafts into orbit. From there, it’s much more feasible to start looking into mining asteroids and building city-ships.
I agree that a Moon colony makes sense, but I think both will happen. What we must see is that our future will take parallel evolutionary paths and that will involve colonisation of planets too, whatever that means. Why not have a permanent settlement on Mars? We have people living in the harshest environments already. It will probably be a good exercise to learn our limits. Maybe we can't have healthy, viable offsprings on Mars and we will settle with cloud cities on Venus.
It's probably not the best idea to pick a winning scenario, let's try everything till we can.
It seems odd to quibble about which rock we should colonize when you think this far ahead.
Any species that lives in a "cloud of orbitals" or a "Dyson Swarm" is going to have colonized other planets in its solar system, if only as a temporary experiment. The thing to do now is push farther out and explore. Any rock will do but Mars has more romance to it and, for better or worse, that's a requirement.
I assume you're saying this in good faith but it's really a straw man argument because it's a false dichotomy. For one there's the obvious: I'm not saying "go nowhere". I'm saying "the Moon makes more sense to colonize than Mars". Also, that doesn't preclude ever colonizing Mars. A Moon-first policy just makes way more sense.
Another flaw: why do we even need to colonize a planet? It actually doesn't make much sense if you really think about it. I'm firmly in the camp that thinks humanity's future is in a cloud of orbitals aka an eventual Dyson Swarm.
It's way more efficient in terms of living area pre unit mass. It requires no energy tech more sophisticated than solar power. It requires no material that we don't already have. You don't have all the problems with getting into and out of large gravity wells. Gravity (ie spin gravity) can be exactly Earth normal.