No, it's merely incredibly difficult. Sustainable living off Earth is far beyond that.
Humans definitely can't leave. Humans are even less well suited to interstellar travel than they are to living at the bottom of the ocean, something they also don't do and have no idea how they could ever do.
So, with tremendous effort humans could visit one of their neighbouring planets. All of these planets are terrible. Mars is by far more hostile to life than anywhere humans have even visited, let alone had a permanent settlement. But we could do it. To what end?
Live here, or die here, those are your options and you should get used to it.
It's difficult, but I don't think it is _that_ difficult. Ecologies, like any living systems, can self-heal and regenerate. There are practices that allows us to tap into that regenerative power as societies. They may not happen fast relative to our individual human lifespan, but 50 years is more than enough time to restore wastelands or reverse desertification.
I don't have a good answer to how sustain an economy based upon mining, refining, and manufacturing things out of mineral resources. Many of us have gotten used to modern conveniences (at its own cost related to mental and emotional health, and social cohesiveness). I think what most people balk on are on the perception of having to go back to barely surviving off the land, or having to alter lifestyle. Lifestyle may have to change, but the same regenerative power of ecologies also gives us significantly more resiliency.
To have the species survive if anything ends all life on Earth - apparently not a priority for you but it is for those that enjoy humanity existing.
Also to explore and learn more about the universe we live in. Do you truly not see value in that? Have you never left the city/state/country you were born in?
> To have the species survive if anything ends all life on Earth
Nothing the universe has thrown at Earth in the past 3 billion years has been capable of ending all life. And nothing that could happen in the next million years seems possible of doing that either.
When we say life on earth we mean human life and civilization. Prokaryotes, while alive, are not really what people mean. Yes they would survive asteroids, nukes, possibly nanobot swarms.
Humans definitely can't leave. Humans are even less well suited to interstellar travel than they are to living at the bottom of the ocean, something they also don't do and have no idea how they could ever do.
So, with tremendous effort humans could visit one of their neighbouring planets. All of these planets are terrible. Mars is by far more hostile to life than anywhere humans have even visited, let alone had a permanent settlement. But we could do it. To what end?
Live here, or die here, those are your options and you should get used to it.