We can do this be sending robots.
True, but there would be less impetus (hah!).
That can be done on the moon for a much lower cost. It might also be economical to return to Earth the things we find on the Moon.
Not quite as it would only be relevant to Mars and a few moons.
I meant 'and everything else' not 'that would be everything'.
Sorry but unless we can create a completely self sufficient colony any outpost will be reliant on re-supply from Earth. Creating a completely self-sufficient colony on Mars would bankrupt any countries that tried it. There will always be some critical material or item that is available only on Earth.
Self-sufficiency is something we'll have to learn how to do. As for bankruptcy, no. Provided things are arranged to give value for money on Earth there is no end to money. Tricky, I grant. Running out of resources could happen.
Mars is not a lifeboat. Until we can get to another star system where we can live on an Earth-like planet long term survival of humans is not ensured.
Yup, but we'll not get there in one bounding leap. It may take generation ships, and if you can do that why do you need a planet?
We need waypoints. Mars may not be optimal or necessary but it is on the way and people can see it in the sky and get excited about it.
Sure, there are more urgent local concerns. The ones you list are good. But if we have the resources there is no need to be constrained by money, we can do a bit of everything. In fact a space colonisation program could yield technological benefits for Earth in all the areas you mention.