I kindly disagree. Nobody wants to live forever on Mars (if you do, you may as well go live in a bunker and never go out, no need to go there). Nobody wants to live forever in a spaceship (for the same reason).
What does that mean? The goal, what people actually want with the "space quest", is to find another planet. Check how far the closest star is (that's more than 4 light years away): we cannot even theoretically go there in any kind of meaningful way, even in the long term.
If your quest is to become a multi-planetary species, you should do theoretical physics on Earth and try to find a way to go that far. No need to solve the engineering problems first, let alone in a resource-intensive and counter-productive way (w.r.t. our survival on Earth).
I find it amazing that engineers don't find it insane to do all the engineering work for something that is, currently, theoretically impossible. It's like building public transportation all over the world based on the idea that we will discover telekinesis ("it doesn't work right now, but as soon as you have telekinesis, it will be great"). Yes it would be cool, but the only sane way to look at it today is that telekinesis is not a thing.
> What does that mean? The goal, what people actually want with the "space quest", is to find another planet.
I highly disagree. After fighting our way out of one gravity well, we shouldn't be quick to jump straight down another (although Mars is certainly easier to get off than Earth).
The spaceship we're currently on makes very inefficient use of material: its shape gives the least surface/livable area; and its density is the highest in the solar system. The resulting gravitational pull makes it very hard to leave: chemical rockets will just about work, but need multiple stages.
In contrast, a more efficient design, like a spin-gravity cylinder inside a hollowed-out asteroid, is much easier to leave (in fact, we'd be flung away, if the floor weren't accelerating us inwards; say, by stepping over a trapdoor!). Whilst such a ship would certainly be more maneuverable than the Earth, it would probably be easier to leave in a convenient orbit (e.g. as a cycler), and use smaller, leaner ships for bespoke travel around the solar system (no point wasting fuel to keep accelerating/decelerating all the gardens, farms, factories, schools, etc. if they're not needed en-route!)
Those things aren't mutually-exclusive though.
Well space research is not a problem, as long as it is research. My problem is that it is becoming a business ("we want to launch a lot of rockets and make money out of it") behind the excuse of "saving the human species and making colonies on Mars".
The space business is a problem for our objective of "surviving sustainably on Earth" (which at this point is synonymous with "surviving on Earth".