To what end?
It’s enormous effort and large fractions of human lifespan to do...what? Don’t get me wrong, I’m as intrigued as anyone. But...to go where? do what? Not warm hypotheticals, but realistic scenarios. Just getting to Mars is like sitting in a small car for 2 years, only to get out in Death Valley - the novelty won’t get you far.
I once calculated, thinking in terms of the “Orion Ramjet” design, how much hydrogen could be scooped up en route to Alpha Centauri. 0.01g per square-meter scoop. Humans just don’t grasp astronomical distances, nor how little there is between destinations.
Asteroid mining? It’s mining. Might be useful and make someone rich.
Mars? Hint: think Antarctic station, but a lot harder to visit and live in.
Moon? We’d be living there if anyone found it interesting enough. We’re not there.
A funny thing, capitalism: a big reality check on what people really want and how much they’re willing to give for it. Space? We’ll see how SpaceX et al do.
Because eventually the rock will be uninhabitable (this is an eventuality, probably not even related to human activity) and if we don’t have a self sustaining subsection of humanity somewhere else none of what we’ve done matters a bit. Anything else we do before then is just steps to get there, like how we needed fishing skiffs before we could build ships that crossed the Atlantic.
To eventually establish self-sufficient colonies that have the potential to be out of reach of the regulations and soul-destroying conformity of any earthly government.
To have a place for our best, smartest and bravest to go where they will not be held back by the stupid and cowardly.