I think that we should consider "the future". Yes, it's intangible but consider this; go back 2 centuries and ask someone if they could setup a business concern which produced millions of widgets a year.
They'd think you daffy.
Now beyond that, ask them to produce any manner of modern device with the precision and high consistency we have. Again, they'd think you mad, and think that such was impossible.
Yet here we are.
The next stage in our development via LLMs is not about AI helping humans. It's about robotics. Automated assembly. Robots (not Androids) able to interact with the environment and able to problem solve akin to say.. a mouse.
Soon, entire factories will be entirely automated. Many almost are. We don't need Von Neumann machines to see this future, but we will certainly have robots capable of building entire factories, collecting resources and processing them, and further building machines to spec. And those machines will be able to self-drive, self-operat autonomously.
Anyone playing typical resource games knows about bootstrapping, but once in the asteroid field we're basically resource infinite. Building engines to attach to asteroids, mining asteroids, building factories to create more robots and engines, all of it will be automated.
We toil at self-driving cars, yet this same tech enables self-driving robotics of all types.
So I honestly think that once we bootstrap in space, this sort of thing can happen fast, fast, fast. Decades to send hundreds of thousands of ice-rich resources to Mars.
The soil? Ah, genetic engineering. Really, this is an entirely new field, and frankly is beyond the danger yet benefit of nuclear science. We have the bomb, yet we have nuclear energy and medicine. Well genetics can obviously be far more deadly, and research all over the world, and startups, are already working on employing bacteria and organisms as self-replicating machines to do our bidding.
The dangers are in our face, but oh well! So if we presume survival, then once an atmosphere is produced we can seed the planet with organisms which can survive on rock and yet work with a mania to process it. It's OK if we immediately have moss like grass substitute everywhere. As long as it's working its magic, we get continued O2 production, and we can always create a rabbit pet or something that licks moss to survive. Or are tasty.
My point is, there are indeed many barriers. But we need to view them with where we will be in decades, not where we are now.