Firstly, I don't think we will ever be capable of destroying the earth, not to the point where it looks anywhere like mars, or comes close to the point of threatening humanity.
Secondly, if humanity goes to mars, we become a multi-planet species, and will go to other planets as well. We are successful if we do so, or more so than if we remain on a well kept earth.
Success is having more humanity, having more power, having more capability to have more people living more lives. Success is not stagnation, while we may find happiness in stagnation, we will find much more in continued growth.
Seven billion members of a modern society, but having created all the issues we face today, is far better than having humanity remain an agrarian society, happy to live little lives and die when plague, injury, or disease wipes them out. I do not believe this is a controversial opinion.
The waste, the pollution, and so on, are necessary byproducts of our system. They always have been since the moment we began to farm, depleting nitrogen from the ground. The emissions cannot be avoided, and the luxuries we live with are human nature, to say we could be "more caring about the earth" is just not true. We can do only two things, stop using resources and have fewer luxuries, or we can reduce the amount of human life to allow the few to have more luxuries.
Neither of those are acceptable, not by my opinion.
is there such a thing as a successful life, and what is it?
This isn't a question of a single person, living in a single moment, in a single civilization. This is looking at human kind. The net result of all our actions. A single life can be lived, in ease, and die, to be successful, but that doesn't make human kind, as a species, successful.
Success, for a species, has always been in population. The more humans we have, the better. It is in adaptability, suitability, in our power to manipulate the world to ensure our species remains on top. Humanity doesn't have feelings, even if it's members do.
but we shouldn't underplay the suffering that capitalism, industry and technological progress have brought and their power to alienate us from our world
What you are doing here, is underplaying the lack of suffering that capitalism, industry, and technological progress have brought. And you underestimate their ability to save our world.
For each day of suffering, people find joy. Even those in the worst conditions will find a way to, at least, ease their pain, to survive another day. A factory worker in China, paid two dollars an hour chooses to live every day. We, as a species, pick suffering over death over and over again. It is clear that we would rather live, for our families, our nations, our communities, than die to avoid pain.
The biggest downfall of capitalism? What? Complaints that things are bad? Yes, they are bad, but they would be worse if capitalism wasn't there. 90% of us would hardly even be alive without technological progress.
And, guess what happens without technology. Humanity lives. We live our happy little lives before we fall to diseases. We have another generation, they live their "happy" lives. This goes on...
Then, after a few thousand years, a meteor hits, the ice age happens, humanity evolves to fit different environments without the boats to see us over the oceans, and planes to connect the different continents. Humanity dies. We lose our planet.
What's the biggest risk with technology, with capitalism? Our planet dies a few thousand years sooner? Is that such a big deal? It was destined to happen anyways, and the way we are going, we are headed to new worlds, we have the minds, the ideas, the technologies to harness power and drive our environment like never before. We track and can counter asteroids, we can see and track when our sun will explode on us. We can leave our planet, go to new ones, colonize them, spread.
And even then, there are seven billion lives today. Without technology, that number could be in the hundred thousands, or millions. Even if we keep that number up for a few million years, there will be more happy homes, more happy lives, more philosophy, more thought, than without technology, even if we destroy our world in doing so.
So, I don't see the downside myself.
Now, do I think this means we shouldn't constantly seek to improve our resource use, to ensure that our world does stay decent? Not at all. I think we should seek to force the development of technologies and enforce regulations that make companies keep reasonable levels of pollution.
We should seek to fix the environment, to end the use of coal, to make new strides in what we can accomplish as a species.
We just shouldn't shoot ourselves in the foot while doing so. We need to instill carbon taxes and enforce new technologies, not encourage people to go back to living lives that they do not consume as much. Whatever we do, we need to ensure that progress is made, not slowed down.